different regions of the earth's surface, and that their resemblances to one another are due to the similar conditions of their new and altered mode of life. Some of these modifications have been acquired (e. g. gemmules) and may be said to be of a positive character, while others are negative, and are due to the disappearance of some of the characters of their marine allies; such is the loss of colour, owing no doubt to the disappearance of the conditions for self-protection which called it into existence. The fresh-water sponges may form the group Potamospongiæ among the Renierinæ.

Three species of the new genus Potamolepis are described: P. leubnitzia, P. chartaria, and P. pechuëlii; they have no resemblance to Spongilla, or indeed to any Renierine sponge. The last species calls to mind a Farrea, owing to the macroscopic structure of its skeleton, and the arrangement of its fibres. The differences appear to be due to their surroundings, for the currents of water in the rainy season being of great force, it is necessary for Potamolepis to develope structures which are not necessary to the Spongilla of stagnant or gently flowing water.

Protozoa.

Parasitic Infusoria.* Trichomonas vaginalis is described by G. Künstler as extremely protean in external form; it may develope pseudopodia over the general surface or localized at the posterior extremity; at the anterior end are four flagella united by their bases, from which point an undulating membrane extends to the posterior extremity of the body. At the base of the flagella also the mouth opens; the nucleus, which varies in form, lies at the side of the cesophagus; the general protoplasm has a vacuolated structure. In the intestine of a certain Chelonian occurs a parasite apparently allied to Giardia agilis. The body is divided into two regions: the anterior is the larger, is vacuolated, and invested by a loose plicated and embossed sheath; the base of the flagellum has almost the same diameter as the body, is very long, and is readily shown to be striated; it reproduces by buds from the anterior extremity. Other organisms are mentioned as parasites, but not described, from the same host. Heteromita or Boda (Bodo ?)-Lacerta is described as a new species from the intestine of Lacerta viridis; the mouth is surrounded by a circular cushion, the nucleus often has a very complicated structure, presenting much variation, the body is areolar; reproduction takes place by transverse fission. A pyriform Flagellate, with four long locomotor flagella, with a lobule at their base, leading into the cesophagus, and a longitudinal costa on the left side, also occurs here. A quadri-flagellate organism with a large posterior vacuole is described from Hydrophilus, also an Amaba, which is truly amoebiform only in the young state, afterwards it maintains a finger-like shape and produces pseudopodia only from the anterior region. Flagellata are also indicated from various insects, from Toxopneustes and the blood of Cuvia, a Nyctotherus from Oryctes and a Planarian from Solen, but with no, or but the briefest descriptions.

* Comptes Rendus, xcvii. (1883) pp. 755–7.

New Infusoria-O. E. Imhof states the discovery in the Lac du Bourget in Savoy of Dinobryon cylindricum n. sp.

A. C. Stokes (of Trenton, N. J.) also records + a Vorticella, which, on account of its peculiar and well-developed external investment, he has named Vorticella vestita.

"Body soft and plastic, broadly campanulate, widest at the anterior margin, constricted beneath peristome border and posteriorly rounded at its junction with the pedicle; when contracted, subspheroidal. The whole cuticular surface is covered by a conspicuous cellular coating which gives the superficial aspect a minutely reticulated appearance, and the external margin a finely crenated outline when seen in optical section. This investment is formed of a single layer of cells arranged in equatorial series, the upper and lower cellwalls being equidistant in each row throughout the whole length of the body. The cells themselves are as colourless as the animalcule and as transparent, their contents being invisible liquid usually containing many dark-bordered, actively moving granules. When the creature is in a weakened or dying condition the cell-contents are so increased in quantity that the cells become extended and bubble-like, the zooid then resembling a mass of froth.

The peristome border is but slightly everted. The vestibular bristle is well-developed and conspicuous. The contractile vesicle pulsates at intervals of twelve seconds. The nucleus is band-like, curved, and remarkably long, one arm extended across the body anteriorly for almost its entire width, then bending and curving for nearly an equal distance along the ventral side of the zooid.

The pedicle is from six to seven times the length of the body, and when retracted forms about seven coils which exhibit transverse striations or wrinkles, particularly noticeable as it is extending. The muscular thread is roughened at irregular intervals by clusters of minute rounded elevations. Body 1/500 in. in height."

W. Milne also records one new genus and four new species from brackish water: Tetramitus gyrans n. sp.; Hexamita Kentii n. sp.; Longicilium flexicuneus n. gen. and sp.; and Tillina barbata n. sp.

Relationship of the Flagellata to Algæ and Infusoria. §-G. Klebs proposes to limit the term Flagellata to the Euglenaceae and Peranemeæ, which are again divided into the Euglenida, Astasieæ, Chloropeltida, and Scytomonadina Stein; and discusses their structure, vital phenomena, and systematic position. The treatise is divided into three sections: (1) monograph of the Euglenacea; (2) some Flagellata in the older sense of the term, belonging to the lower chlorophyllaceous algæ; and (3) the fresh-water Peridineæ.

The Euglenaces are made up of the genera Euglena, Trachelomonas, Colacium, Ascoglena (Stein's Euglenida), Eutreptia, Phacus, Astasia, Rhabdomonas (two species of Stein's Astasies), and Menoidium

* Zool. Anzeig., vi. (1883) pp. 655-7.

† Amer. Mon. Micr. Journ., iv. (1883) p. 208.

Proc. Phil. Soc. Glasgow, xiv. (1883) pp. 32-6 (1 pl.).

Sep. repr. from Unters. Bot. Inst. Tübingen, i. (1883) 130 pp. (2 pls.). See

Bot. Ztg., xli. (1883) p. 595.

Stein. The chlorophyllaceous are separated from the non-chlorophyllaceous hyaline Euglenaceæ. The author describes their general structure, system of vacuoles, contents, and investing structures, and then proceeds to their mode of division, resting condition, and the question of sexuality, as to which he obtained simply negative results, and the general biological phenomena of the green Euglenaceæ. He considers the colourless as direct descendants of the green forms, and as the link of relationship of the latter with other Flagellata. No systematic separation of the hyaline from the green forms is possible. Notwithstanding the numerous transitional forms between the different species of Euglenaceæ, the author establishes two groups with nine genera, the characters dependent on the delicate internal structure, the mode of movement, behaviour towards external influences, &c. The author then discusses the relationship of the Euglenacer to the Peranemeæ and Algæ. The Peranemeæ resemble the Euglenaceæ in essential points, but differ in the possession of a mouth-opening and special mouth-apparatus.

Among the Flagellata of Stein, the author regards, in addition to the Volvocineæ, Chlorogonium euchlorum Ehbg. as a typical Chlamydomonad, as also Chlorangium stentorinum from the family of Hydromorina. As is the case with the other Chlamydomonads, hyaline forms of both occur. A new classification of the unicellular Chlorophyceae is proposed, associating under the name Protococcoides the groups Pleurococca, Chlorosphæraceæ, Tetraspore, Chlamydomonadæ, Vlvocineæ, Endosphæraces, Characies, and Hydrodictyeæ. The Endosphærace, Tetrasporeæ, and Chlorosphærace lead to the Siphoneæ, Ulvacea, and Confervaceæ.

The fresh-water forms of the Peridineæ, on the vegetable nature of which the author agrees with Leuckart, are treated of in detail, and the following are the general results at which the author has arrived.

The Euglenacea and Peranemeæ must be separated from the Ciliata and placed among the Infusoria, forming a separate division, the Flagellata, distinguished by a different mode of ciliation, and other differences in structure. The Volvocineæ, Chlamydomonadæ, and Hydromorina Stein remain partly among the Chlorophyceæ. From both the Ciliata and the Flagellata must also be separated the Peridineæ, termed by Claparède and Lachmann Cilioflagellata, and regarded by Bergh and Stein as a connecting link between these two groups; they form a well-marked family of Thallophytes.

Klebs' group of Flagellata remains, even if associated with the Infusoria, an intermediate group, connected on one hand, through the Cryptomonadæ, with the Algae, on the other hand with the Vampyrellæ, rhizopod-like organisms, Noctilucæ, &c. Their general character connects them partly with the Protozoa, partly with the lower Thallophytes.

Transformation of Flagellata into Alga-like Organisms," A paper intended to show some relations between animals and plants at their lowest degrees of development is contributed by M. Shmankevitch.

* Mem. Novorossian Soc. Natural., vii. Cf. Nature, xxix. (1884) p. 274.

When the Flagellate Anisonema acinus-having a relatively high organization-is cultivated for many generations in a medium which is slowly modified, for instance in fresh water to which a certain amount of sea-salt is added, its structure is modified in proportion as the concentration of the solution of salt is increased. The individuals become less developed, their size diminishes, and the feedingcanal loses its former development. Numberless intermediate forms between Anisonema acinus and its new, less developed representatives, make their appearance, as well as between these and the still lower Anisonema sulcatum, which would thus be but a lower organized variety of the former. When the concentration of the medium in which the Anisonema lives is carried on side by side with a change of temperature of the medium, the transformation goes further on, and the lowest Anisonema are transformed on the one side into alga-like organisms, and in another direction into organisms which seem to belong to the category of fungi. The individuals not only become smaller, but they give rise also to a progeny long before reaching their full size. Under the influence of the sun's rays the uncoloured Flagellata acquire a new physiological function, and develope chlorophyll.

"We see thus," the author says, "the beginnings of two kingdoms, animal and vegetable, radiating from one common stem. We see the transformation of one of them into the other, not only in its morphological features, but also in its physiological functions, under the direct influence of physical and chemical agencies. The saline solutions, as compared with fresh water, diminish the size of the lower organisms, and at the same time they contribute towards the development of chlorophyll in the fresh-water alga, thus giving them, so to say, a more vegetable character, together with an increased productiveness." And further: "Whilst descending from Anisonema sulcatum to a unicellular alga, we see the retrogressive development, simplification of organization; we descend towards the plants containing chlorophyll. . . . While descending from the same Anisonema by another branch, we enter into the region of those lower organisms which, under the influence of another medium, do not develope chlorophyll, and, having no nutrition from the air, derive their food from the substratum; they might be described as parasitic Rhizopoda, and this the more, as from the fungoid form we can ascend, under some circumstances, not only towards the amoeba-like uncoloured Flagellata, but also towards the moving monad. On the contrary, by reversing the physical agencies, we can arrive, from the unicellular alga, as well as from the fungoid form, to an uncoloured form having the structure of Anisonema." The researches of A. Giard, Cienkowsky, and Famintzin, and some observations by E. Ray Lankester, seem to be, in the author's opinion, in accordance with the above.

Stein's 'Infusionsthiere.'*-The second half of Part III. of Dr. F. Ritter v. Stein's well-known work on the Infusoria, has just been

*Stein, F. Ritter v., Der Organismus der Infusionsthiere. III. Abth. II. Hälfte. Der Organismus der Arthrodelen Flagellaten.' fol., Leipzig, 1883, 30 pp. and 25 pls.

published. It does not contain the expected characters of the genera and description of the species figured in the first part, which are still further deferred, but deals with the forms most of which are more usually known under the name of Cilio-flagellata.

After a descriptive account of the course of his researches since the publication of the first half in 1878, the author gives a summary (in 23 pages) of the results at which he has arrived. The forms now treated of he considers to be a sub-order of the Flagellata, the simpler forms of Flagellates described by the first part forming the other suborder. The latter he terms Monero-flagellata and the former Arthrodelo-flagellata. He objects to the name of Cilio-flagellata, as it supposes that the organisms besides a flagellum are provided with cilia, whilst Prorocentrum and Noctiluca are without such cilia. They all, however, have a distinctly articulated body, whence the designation Arthrodelo.

The division into five families is founded upon the modifications of the articulation, and the 30 genera upon the absence or presence of a secondary articulation of the body-covering as well as on their arrangement, number, form, and size. The following are the families and genera:

Prorocentrinæ (Prorocentrum, Dinopyxis, and Cenchridium), Cladopyxide (Cladopyxis), Peridinidae (Gymnodinium, Hemidinium, Glenodinium, Clathrocysta, Heterocapsa, Amphidoma, Oxytoxum, Pyrgidium, Ceratocorys, Goniodoma, Gonyaulax, Blepharocysta, Podolampas, Diplopsalis, Peridinium, and Ceratium).

Dinophyside (Amphidinium, Phalacroma, Dinophysis, Amphisolenia, Citharistes, Histioneis, and Ornithocercus).

Noctilucida (Ptychodiscus, Pyrophacus, and Noctiluca).

Being prevented by unfavourable weather from going to the sea, Dr. Stein bethought himself of trying the contents of the stomachs of marine animals preserved in spirit, and in this line of research he was completely successful, by far the most numerous and important of his discoveries being obtained from the stomachs of various Tunicates (Ascidia, Salpa, and Cynthia), Vermes (Sabella, Serpula, and Sipunculus), and Echinoderms (Synapta, Ophiothrix, Comatula,' and Actinometra). Hundreds of individuals were obtained from one species of Salpa, and the author was occupied from November 1880 to the end of 1882 in the examination of the organisms he thus found.

A general description is given of the principal forms, with references to the 25 plates, which are also accompanied by brief "explanations." It was not found possible to engrave all these on copper as was done in the case of the plates of the preceding Parts, and 11 are accordingly lithographs.

It will be observed that Stein includes Noctiluca in his order of Arthrodelo-flagellata. His justification for this we propose to deal with later, but here may be mentioned that it is based on the discovery of the forms placed in the two genera Ptychodiscus and Pyrophacus, which on the one hand are closely related to Noctiluca while on the other they are unmistakably Arthrodelo-flagellates.