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accumulation (which Dr. Newberry calls the grist' of the continental ice-sheet) is about sixty feet; though in places at the very border, as at Adelphi, in Ross county, it is two hundred feet. Granite bowlders from northern Canada are found all the way down to this limit, but not beyond it. There is a granite bowlder at Lancaster 18 x 12 x 6 feet. The glaciated portion of Ohio is level, and univer

crop-reports show that the average production of wheat per acre is nearly twice as large in the glaciated as in the unglaciated portion of the state.

Professor Wright's investigations fully confirm the surmise of Professor Shaler, that, during its greatest

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sally fertile. This is in part owing to the diversity of rocks ground up by the advancing ice, and in part to the fact that it was pulverized by mechanical action, and is spread evenly over the surface. South of the line the country is cut up into gorges; and, as a rule, the soil is shallow and comparatively sterile. Scratched stones are entirely absent, and granite is found only in the river-valleys. The

ice of the glacial period crossed the Ohio River at Cincinnati, and extended a few miles south. From this, some interesting conclusions follow. The Ohio River, through its entire course, occupies a valley of erosion, having, for more than a thousand miles, cut a gorge from three hundred to five hundred feet deep through the horizontal strata of the coal-formation. ing the extension of the glacier into Kentucky; this cañon of the Ohio must have been filled with ice at Cincinnati, forming a barrier in the

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river nearly six hundred feet in height. This would form slackwater in the Ohio all the way up to Pittsburg, submerging the site of that city to the depth of two hundred and fifty or three hundred feet, and setting the water back far into the valleys of the Alleghany and Monongahela Rivers.

In the extensive gravel-deposits of Ohio, south of the glacial line, no paleolithic implements have as yet been found; but they may be confidently looked for. When they are found, the investigations of Professor Wright and his associates will have important bearings in determining their age; for, in many respects, Ohio affords unrivalled opportunities for determining the amount of erosion which has taken place since the ice of the glacial period withdrew. So far, the evidence points to a later date for the glacial period than that which is advocated by some. The erosion which has taken place since the glacial period is surprisingly small. The streams running over the glaciated surface occupy very shallow valleys. In those rivers whose course was changed by glacial action so as to produce waterfalls the gorges are never more than a few miles long. The period cannot have been extremely long, or these streams would have done more work.

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of homes, to imperilled health and comfort, and to business delayed, cannot be estimated, but are known to have been very extensive. A very full report is given in the Monthly weather-review of the signal-service.

The month has been colder than the mean for the region west of the Mississippi River. The mean temperature was from 8° to 16° below the normal on the Rocky-mountain plateau; it was slightly below the normal in the north, east of the Mississippi; and above the normal in the south. In the whole country east of the Rocky Mountains the temperature was 0.5° below the normal. The lowest temperature reported was -57°, at Fort Washakie, Wyoming. The rainfall of the Pacific during the winter has not been sufficient to assure a medium wheat-crop in that region. The deficiency was over 4 inches in central California and Oregon in February, and there were larger deficiencies during the previous winter months. This important crop, therefore, depends largely upon the spring rains, which in this region are usually very light. On the other hand, there has been a large excess of rain in the lower lake-region and Ohio valley, the excess in the latter region being 3.86 inches.

Ice dangerous to navigation is slowly drifting south to latitude 43°, between longitudes 45° and 48° W.

The chart on the next page shows the mean distribution of air-pressure and temperature, with the prevailing wind-directions in the United States and Canada. This chart shows very high pressure over nearly the whole country, it being from .1 to .2 of an inch above the mean, except in Florida and southern California. The areas of low pressure traced to the Atlantic have all passed over the St. Lawrence valley, and in no case has the centre of any depression passed to the south of the Ohio valley or middle states.

The total number of storms that have been traced in the United States during each February since 1877 is given below. The mean velocity of the storms, as published in the annual reports of the chief signal-officer, are added for comparison.

Date water reached the danger

line.

Date water left the dangerline.

Am't. Date.

Feet.

4.8

5

13

12

16.3

15

22

14

1

15

16

100,000

Year.

20.4

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1878

8

27.8

13

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month.

Still rising

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28

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24

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Pittsburg, Penn..
Marietta, O.
Maysville, Ky.
Cincinnati, O..

Lawrenceburg, Ind.
Vevay, Ind.
Jeffersonville, Ind..
Louisville, Ky.
New Albany, Ind.
Shawneetown, Ill.

Cairo, Ill

Memphis, Tenn.. Vicksburg, Miss.

The last column contains losses only so far

as reported. The injuries due to sweeping away

No. of storms.

Mean velocity, miles per hour.

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FEBRUARY, 1883.

REPRINTED IN REDUCED FORM

BY PERMISSION OF THE CHIEF SIGNAL-OFFICER. MONTHLY MEAN ISOBARS, ISOTHERMS, AND WIND-DIRECTIONS,

Ten storm-tracks were traced across the ocean. Of these, a very severe one was felt in the north Atlantic from Feb. 4th to 7th. The winds were of unusual severity, and pressures as low as 28.1 inches were reported by several steamers. This storm, however, was exceeded in extent and severity by most violent gales from the 12th to the 16th, when pressures below 28 inches were recorded.

The total movement of the air on Mount Washington (as indicated by a specially devised Robinson's anemometer) was 32,404 miles, there being 1,825 miles on the 17th. Winds over 100 miles per hour were reported on the 1st, 17th, 26th, and 27th.

Ninety-two cautionary signals were displayed during the month; of which 75, or 81.5%, were justified by winds of at least 25 miles per hour within 100 miles of the station.

The most extensive auroral display was that of the 24th, which was observed on the NewEngland coast, and from the upper Mississippi to Washington Territory. Auroras are also reported on the 1st, 4th, 5th, 13th, 25th, 27th, and 28th. Prof. D. P. Todd of Amherst reports sunspots most numerous on the 12th and 13th, and least on the 23d and 24th. Unusual earthquake-shocks were experienced on the 4th in Illinois, Michigan, New Hampshire, and Maine. It would seem, that, at the same time, shocks were felt in Agram (Hungary) and Madrid (Spain), as cabled to the New-York Herald. On the 27th another notable shock was felt in Connecticut, Rhode Island, and Massachusetts.

THE LAW OF NUCLEAR DISPLACE-
MENT, AND ITS SIGNIFICANCE IN
EMBRYOLOGY.

DURING his investigations upon the development of fishes, mollusks, and arthropods, the writer's attention has been drawn to the physiological relations of the food-yelk, and the germinal matter of the ova of these forms. A more thorough study of the relations of the two principal materials of the ova of various forms has led him to the conclusion that there is a general law which largely, if not entirely, determines the mode of cleavage apparent in various embryological types. Approximations towards a general statement of the law have been made by Von Baer, Haeckel, Balfour, Whitman, and Mark. My only object is to present what I believe to be some new evidence, and to extend the scope of what appears to be an important generalization.

ova. These are, first, the holoblastic or evenly segmenting, and, secondly, the meroblastic or unevenly segmenting. The so-called centrolecithal type is found almost altogether amongst the arthropods, and seems to be in a great measure characteristic of them; but, upon close examination and comparison, I believe it will be found that this mode of segmentation is not so widely different from that met with in the ordinary meroblastic ovum. Whatever may be the opinion with regard to the claims for the recognition of two or three types of segmentation, there can be but two forms of ova discriminated in the animal kingdom; viz., those with, and those without, a food-yelk. Those without food-yelk may be called homoplastic; that is, they are composed of but one kind of plasma, all of which is germinal. The first segmentation-nucleus is central in position after fertilization, so that the first cleavage divides the ovum into two equal segmentation-spheres. The result of further segmentation is to divide the total germinal mass into tolerably evensized spheres. The other type, opposed to the foregoing, may be called the heteroplastic, by which it is intended to signify that two or more proteids may enter into the composition of the egg, besides oils in the form of drops. At the time of maturation and impregnation the nucleus is displaced from its original central position to a remarkable extent; in fact, it may be so displaced, as compared with its position in very young eggs, as to appear as if it were altogether superficial or parietal; as in the large ova of fishes, reptiles, and birds. This parietal position of the first segmentationnucleus is not its original one, as an investigation of the developing ovules in the ovaries of these forms will show; but, even long before the first segmentation-nucleus is formed by the fusion of the male and female pronuclei, we actually find, that in some cases the germinative vesicle has migrated from the centre of the ovum, towards the periphery, without having suffered any marked change in size.

To what cause is this permanent displacement of the egg-nucleus due? We find it to occur only in those ova in which we may detect two sorts of plasma, or in those with germinal matter to which a second or passive quantity of matter has been added during the intra-ovarian growth of the egg. The added material may be in the form of a clearly defined yelk, or it may make its presence manifest only after the beginning of segmentation, by aggregating at one pole or centrally as a less homogeneous, more granular mass than the portion directly There are only two clearly marked types of involved in the process of segmentation.

The

germinal matter, protoplasm of the egg, is the self-motile part. The yelk or deutoplasm, on the other hand, is often composed of spherules, granules, plates, or oval bodies, and is converted by metabolic processes into the first during the later stages of development. The first is the potential part of the egg: the latter is the passive and nutritive. Wherever the yelk is greatly in excess of the germinal matter, the embryo is often far developed, as regards morphological details, before the deutoplasm is nearly all absorbed, its final absorption being accomplished largely through the intermediation of the vascular system of the embryo; as in the ova of fishes, birds, and reptiles. The greater the mass of the yelk in proportion to the bulk of the germ, the more extensive is the permanent displacement of the nucleus from its original central position as observed in the young ovicell. The displacement of the nucleus, or germinative vesicle, would then appear to be due to the development of the yelk as a deposit of material of a lower grade of differentiation than the germinal protoplasm in the central part of the egg, as in meroblastic and centrolecithal ova, from the central portion of which the nucleus has been repelled, and taken up into the germinal matter.

In the eggs of osseous fishes it is certain that the protoplasm, or germinal matter, is arranged on the outside of the yelk, or deutoplasm, in some cases, or sends down processes or a meshwork into the latter, prior to the time of the formation of the germinal disk; so that the teleostean ovum actually passes through a centrolecithal stage. In birds and reptiles, this probably occurs during late intra-ovarian development, as impregnation must occur before encapsulation in the shell, which is formed in the oviduct after the albumen, or 'white,' has been added. Every grade of proportion, from a very small quantity of deutoplasm up to an excessive amount as compared with the germinal protoplasm, may occur; so that no sharp line of demarcation exists between truly holoblastic and truly meroblastic ova. The degree of inequality in the segmentation is therefore, generally speaking, dependent upon the amount of deutoplasm, or food-yelk, which is present, and the degree to which the germinative vesicle has been permanently displaced from its central position. This is, however, qualified by certain secondary modifications, to be discussed at the end of this paper.

This principle accounts for all the forms of unequal segmentation, even including the centrolecithal, where the peripheral segmentation

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The expulsion of the germinative vesicle from the centre of an evenly segmenting egg, to develop the polar cells, is not to be confounded with the movement of the nucleus towards the periphery of the ovum while still in its follicle, in the large-yelked meroblastic type. The distinction between these two cases, I believe to be fundamental. In the ovum of Ostrea, Unio, Mya, etc., the nucleus at the time of the emission of the egg is still approximately central in position, although the ova are slightly meroblastic; while in Lepidosteus, for example, the nucleus of the nearly mature ovarian ovum is actually peripheral, but has not yet been broken up, or lost its form. Moreover, in the holoblastic type, the nucleus, after its metamorphosis and conversion, in part, into the first segmentation-nucleus, is again repelled towards the centre of the egg, a phenomenon which does not occur in any meroblastic ovum with a germ-disk of relatively small dimensions, lying upon a disproportionally large yelk. This is a vital distinction, and one which, as far as I am aware, has not been insisted upon in the discussion of nuclear movements. A few illustrative diagrams from the actual subjects will make my meaning much clearer.

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Fig. 1 represents an ovicell from the ovary of the common eel, enlarged ninety-six times to show the nucleus (n) in a nearly central position, with a very large number of very small, globular nucleoli adherent to its walls. The surrounding plasma (p+d) may be taken to represent both protoplasm and deutoplasm, but in a still undifferentiated state. Fig. 3 is an ovarian ovum of the bony gar (Lepidosteus osseus), very nearly mature, without its granulosa or follicle represented, enlarged seven times. The nucleus (n) in this section has approached the surface of the egg, and is almost or quite in contact with an almost homogeneous outer protoplasmic layer (b) just within the zona radiata (a). Upon examining the material contained within the inner edge of the protoplasmic layer (b), we find that still another differentiation of the egg-substance has occurred by which a portion (p) on either side

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