elevated stations, will be needed before these formulae can be improved.

The following directions may be given as essential to the satisfactory working of the dry- and wet-bulb hygrometer:

In order to obtain accurate results, an induced air-current from 1.5 to 5 metres per second (3.4 to 11.2 miles per hour) is essential. This is needed even with moderately high wind; as experiment has shown, that, in a double-louvred shelter, with a wind of 12 miles per hour blowing directly through it, a velocity of only 1 to 1.5 miles per hour was recorded in the most favorable spot.

The thermometers should be preferably cylindrical, with the bulb removed an inch or more from the scale; and no metallic substance should be permitted near the wet bulb. The dry thermometer should be kept clean, as dust and grit would cause a deposition of moisture in foggy weather.

The muslin should be fine, and tied smoothly over the bulb. It needs cleaning as often as it appears to be turning yellow. If dust settles upon it, it can be easily cleaned with water.

Clean rain or melted-snow water should be used for wetting. A strip of cotton three

eighths of an inch wide, or a wick, will serve to make connection between the muslin and the reservoir in warm weather. If the air is very dry, this strip will cease acting; and in such case the bulb may be immersed for a moment. It will be found, that if the reservoir is kept full, and the angle of the cotton is not too great, the latter difficulty will seldom be encountered.

If any moisture is seen on the dry thermometer, it should invariably be wiped off.

If the air-temperature approaches freezing, the reservoir should be removed; though the wick may be left, its end being carried up and fastened to the frame in such a way as to permit of immersing the bulb. The water in the reservoir should be kept in the open air until a film of ice forms upon it, the intention being to keep it as near freezing as possible. The bulb should be repeatedly wet by immersion till a coating is formed, the thickness of which should depend on the difference between the dry and wet bulbs and the velocity of the air-motion; i.e., the greater the difference and the velocity, the thicker the coating. There is no difficulty with an induced air-current in obtaining accurate results with a coating 1 mm. in thickness.

If ice is found on the bulb with an air-temperature at or above freezing, it may be evaporated by the air-current, or melted off with water. The former method is preferable if the wet-bulb temperature is below freezing. If, on immersing, a drop is found at the bottom of the bulb, it can be easily removed before it freezes by touching with the edge of the reservoir.

With these precautions, an accurate determination of the moisture in the air may be made; and this must necessarily add to the value of hygrometric observations, which are so important in the study of the progress and development of storms. H. A. HAZEN.

A STUDY OF THE HUMAN TEMPORAL

BONE.1-III.

THE temporal bone at birth consists of three osseous pieces suturally connected and partially anchylosed, but readily separable. The pieces are named the squamosal, petrosal, and tympanal bones. In some animals they remain permanently distinct, and in others are variously anchylosed. The squamosal and petrosal correspond in the main with the squamous and petrous portions of the temporal as usually described; but the so-called mastoid portion is derived from both the former. The squamosal contributes about one-third to the mastoidea, while the petrosal contributes the remainder.

The squamosal is a nearly circular upright plate which joins the petrosal at the petrosquamosal suture. This appears internally as a fissure, extending from the notch at the lower border of the squamosal, in front, to the notch at its border behind. Externally it descends from the latter notch to a position just behind the tympanal.

The mastoid portion of the squamosal is proportionately larger than later, and its auditory plate is less distinctly differentiated from the general plane of the bone. Internally it is defined by a shelf on which rests the contiguous border of the tegmen of the petrosal. Below the shelf, the auditory plate exhibits the smooth surface of the scute, which forms the outer boundary of the attic of the tympanum. The cellular portion above and behind forms the outer boundary of the mastoid antrum. articular surface for the lower jaw is a shallow concavity, with scarcely a distinction of glenoid fossa and articular eminence; and it deviates relatively little from the general plane of the squamosal.

The

The petrosal obscurely displays the labyrinth, already of mature size and bounded by compact

1 Concluded from No. 17.

walls, embedded in more spongy substance, from which it may be readily excavated. The superior semicircular canal is especially conspicuous, and includes a large recess, which is subsequently obliterated. The tegmen appears as a distinct triangular plate projecting from the petrosal and overlapping the shelf of the squamosal. The tympanic cavity with its attic and the mastoid antrum are well produced, and are of nearly mature size.

The mastoid portion of the petrosal extends behind that of the squamosal, and is commonly partially anchy losed with it. Its upper extremity is notched to a variable degree; and its lower part exhibits a comparatively slight eminence, premonitory of the future conspicuous mastoid process.

The tympanal1 is a horseshoe-like bone, with its ends anchylosed to the auditory plate of the squamosal. From this it slants downward and inward, and is suturally connected along its posterior and lower border with the petrosal. Its inner margin is grooved for the insertion of the tympanic membrane.

In the development of the temporal bone, the squamosal and tympanal are produced from fibro-connective tissue, and the petrosal and styloid process from cartilage. Össification commences in the squamosal about the close of the second month of embryonic life; a centre appearing at its lower part, and extending upward in the squamous and mastoid portions, and outward in the zygomatic process. The following month, a centre appears in the lower part of the tympanal, and grows into a slender ring, incomplete above. Ossification commences in the petrosal near the middle period of foetal life. Two centres appear, and extend in the walls of the labyrinth. These centres have been appropriately named by Professor Huxley the prootic and opisthotic. They quickly coalesce to form the labyrinth, by the subsequent continued growth of which the pyramidal and mastoid portions of the petrosal are developed.

The prootic produces all that portion of the petrosal seen within the cranial cavity, except that which is contiguous to, and forms, the jugular fossa. It gives rise to the upper part of the cochlea, including its base and cupola ; to the internal auditory meatus, the upper part of the facial canal and its hiatus, the upper part of the oval window, the superior and external semicircular canals, the upper arm of the posterior semicircular canal, and the tympanic tegmen.

The opisthotic produces all the petrosal seen 1 Auditory process, annulus tympanicus.

beneath the cranium. It gives rise to the lower part of the cochlea, the promontory and lower part of the oval window, the round window, the lower arm of the posterior semicircular canal, the lower part of the facial canal, the jugular fossa, the carotid canal, and the floor of the tympanum.

The mastoid portion of the petrosal is produced, subsequent to the complete coalescence of the prootic and opisthotic, by outgrowths from the posterior and external semicircular canals. The outgrowth from the posterior semicircular canal first shows itself externally in the broad plate of cartilage which forms part of the cranial wall between the squamosal, the parietal, and occipital bones. It makes its appearance as an elliptical islet just in advance of the occipital. In this condition it has been viewed by Professor Huxley as a distinct ossific centre, to which he has given the name of the epiotic, regarding it as the specially mastoid part of the mastoid portion of the temporal bone. In my preparations, the elliptical islet has appeared as a continuous growth from the most prominent part, outwardly, of the posterior semicircular canal, after the completion of this by the co-ossification of its arms, which spring separately from the prootic and opisthotic. Later, a second element of the mastoid portion of the petrosal, as an outgrowth of the external semicircular canal, makes its appearance as a quadrate islet in the cartilage intervening to the elliptical islet and the squamosal. The two islets quickly unite, and thus together form the mastoid portion of the petrosal; the notch between them, above, still remaining at the upper extremity of the latter, at birth. From the anterior or quadrate islet, the mastoid process is subsequently developed, and not from the supposed epiotic, as has been asserted.

The squamosal and petrosal commonly anchylose in the external portion of the petrosquamosal suture, near the time of birth; and this portion of the suture is usually obliterated during the first or second year subsequently. Sometimes traces of it remain as irregular chinks, and rarely the greater extent or the whole of it may be retained, as represented in the accompanying fig. 3, from one of several similar specimens in the university museum. The suture is observed to descend from the notch at the upper border of the bone to the point of the mastoid process; and it thus indicates that the anterior third of the mastoidea pertains to the squamosal, while the rest alone belongs to the petrosal. The internal portion of the suture, commonly after some years, is

but partially obliterated, and frequently remains, to a variable extent, as a fissure defining the tegmen of the petrosal from the inner surface of the squamosal.

The mastoid process, scarcely marked at birth, becomes conspicuous only after a year or two. The mastoid antrum is developed at birth; but the surrounding mastoid cellules undergo but little development until after puberty.

The external auditory meatus is produced after birth. The auditory plate forming its roof is gradually more differenti

ated from the rest of the squamoŝal, and its tympanic scute becomes more distinct by the production of spongy substance between it and the roof of the meatus. The floor and sides of the latter are produced from the tympanal ring, which becomes the tympanic plate of the more mature bone. Lateral processes grow outwardly from the ring, expand at the ends, and conjoin to form the auditory process, leaving an aperture in the tympanic plate. The aperture is obliterated about the third or fourth year, but occasionally is retained as an imperfection, closed by fibrous membrane. From growth downward and backward from the tympanal, the vaginal process and posterior extremity of the tympanic plate are produced. JOSEPH LEIDY.

FIG. 3.-Temporal bone, one-half size,

exhibiting the outer part of the petrosquamosal suture, permanently retained, and indicating the division of the mastoidea into a squamosal and a petrosal portion.

THE NAPLES ZOOLOGICAL STATION.1 II.

THE fleet of boats belonging to the station, to whose efficient services the constant supply of material is due, consists of two steamlaunches and a number of row-boats and sailboats. The larger of the steamers, named, after the great German biologist, Johannes Müller,' was given by the Berlin academy of sciences; while the smaller, the Francis Balfour,' was bought by the station. These are used for long excursions, being absent in summer sometimes for three or four days.

1 Concluded from No. 17.

The smaller boats are used for shorter distances and for surface-netting, by which is obtained the heterogeneous collection of large and small pelagic animals known as auftrieb, and brought into the station every day in fair weather. A vessel full of the auftrieb is taken to the occupant of each table in order that he may search for free larvae, if he happens to be studying the embryology of animals which leave the egg at an early stage, or may study the many curious pelagic animals which cannot be kept in captivity, and only occur from time to time in the contents of the surface-nets. The larger pelagic animals-such as large medusae and ctenophores-are separated from the auftrieb for the use of those who happen to be specially engaged in their study. But among the many minute creatures which are to be found in it at various times may be mentioned the winged, free, swimming mollusks of the class Pteropoda, known to the Neapolitan fishermen as farfalle di mare, or sea-butterflies; the other class of free, swimming mollusks, Heteropods; the free, tailed ascidians, Appendicularia; innumerable species of small medusae, - some adult, some the young stages of the fixed Hydrozoa; and transparent crustaceans of various sizes of the class Copepoda, which are never wanting.

The greatest possible care and attention is given by the attendants, and by the gentlemen of the staff, to the requirements of each zoölogist in the station, with respect to material. If unfavorable weather prevents fishing-opera

tions, or if the animals required are rare, whatever is at hand in the preserved state is placed at the disposal of the investigator; and advice as to methods of preservation and treatment, and information as to the breeding-times and seasons of frequency or rarity of the inhabitants of the gulf, are always offered with the greatest freedom and courtesy. By writing beforehand, a naturalist about to work at the station may insure having material-living and preserved, adult and in the young stages - ready for him on his arrival, so that he can commence his researches at once. But the zoologist who occupies himself at the station is not merely a passive recipient of the benefits of its organization. Every opportunity is given to him to study its whole working, and to take an active part in the fishing and dredging operations. He is invited to accompany the members of the staff on the steamers on excursions in the bay and to various points on the coast or neighboring islands, to the Bay of Salerno, to Capri, to Ischia, in order to see how the different kinds of apparatus are worked, and, if he pleases, to descend, equipped in the diving-dress, and examine the bottom of the sea with his own eyes. beauty of the scenery and climate, the congenial society, and the interest attaching to the operations, combine to render these excursions the most pleasant events in the course of a visit to the zoological station.

The

A zoologist obtains the privilege of working at the station by application to some institution

in his own country which has the disposal of a table in the majority of cases, the application has to be made to the government. The station lets its tables to scientific corporations or to governments at a yearly rental of four hundred dollars each. There are, at present, twenty tables taken, of which the greater number belong to Austria, Germany, Russia, and Italy. Holland and Belgium have one each, and England has two. There is room in the station for thirty. The rapid development of the institution is shown by the fact, that, when it was first opened (in January, 1874), only seven tables were taken. About two hundred and thirty biologists-among them, very many of the highest eminence - have worked in the laboratories of the station in the nine years of its existence; and the published works founded on the studies so carried out form a considerable proportion of the total addition to biological knowledge, produced during that period. The brilliant researches of Francis Balfour on the development of elasmobranchs, which formed such a large step in the progress of vertebrate embryology, were carried out chiefly during the time he spent at the table of Cambridge university, in 1874, 1875, and 1877; and he always fully acknowledged the debt he owed to the zoological station and its staff. Professor Grenacher commenced his researches on the eyes of arthropods at the station in 1876, researches which resulted in his classical work, which is, up to the present, the principal authority on the subject. The brothers Oscar and Richard Hertwig carried out their interesting work on

the histology of the Actiniae at Naples. F. E. Schultze and Oscar Schmidt, two of the principal living spongiologists, have availed themselves of the resources of the station; and Professor Claus, Dr. Hubrecht, Dr. Spengel, and Dr. Chun are other names whose celebrity in zoölogy is connected with the institution. Last year an American zoologist, Dr. Whitman, carried out some important researches in the Naples laboratory on the curious parasites, Dicyemidae.

The number of those belonging to the permanent scientific staff of the station is eight, including Mr. Petersen, the engineer, to whose skilful and successful management of the machinery the wonderful regularity and efficiency of all the mechanical arrangements is due. The other seven are biologists who are occupied in the preparation of monographs of various classes, for the series published by the station; while they divide among them the work connected with the issue of the two periodical publications, and the routine duties of the laboratories. Dr. Dohrn acts as director, and represents the station to the outside world; while the chief duties of management devolve on Dr. Eisig, to whose devotion and foresight the enterprise owes much of its success. The duties of librarian are discharged by Dr. Brandt, whose name is well known in connection with the recent discoveries that have been made, as to the existence and significance of symbrosis in animals, and who is engaged at present on the monograph of the radiolarians of the gulf. Dr. Lang, in the