April 13, 1883.] 



SCIENCE. 



273 



Ten storm-tracks were traced across the 

 ocean. Of these, a veiy se%'ere one was felt 

 in the north Atlantic from Feb. 4th to 7th. 

 The winds were of unusual severity, and press- 

 ures as low as 28.1 inches were reported by 

 several steamers. This storm, however, was 

 exceeded in extent and severity hy most vio- 

 lent gales from the 12th to the 16th, when press- 

 ures below 28 inches were recorded. 



The total movement of the air on Mount 

 Washington (as indicated b}' a specially de- 

 vised 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 displaj'ed 

 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 displaj' was that 

 of the 24th, which was observed on the New- 

 England coast, and from the upper Mississippi 

 to Washington Territor}-. Auroras are also 

 reported on the 1st, 4th, 6th, 13th, 25th, 27th, 

 and 28th. Prof. D. P. Todd of Amherst re- 

 ports sunspots most numerous on the 12th and 

 ISth, 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 (Hungarj") 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 develop- 

 ment of fishes, moUusks, and arthropods, the 

 writer's attention has been drawn to the phj'sio- 

 logical relations of the food-yelk, and the germi- 

 nal matter of the ova of these forms. A more 

 thorough studj- of the relations of the two prin- 

 cipal materials of the ova of various forms 

 has led him to the conclusion that there is a 

 general law which largely', if not entirely, deter- 

 mines the mode of cleavage apparent in various 

 embrj-ological tj-pes. Approximations towards 

 a general statement of the law have been made 

 by Von Baer, Haeckel, Balfour, Whitman, and 

 Mark. TSly onlj' object is to jDresent what I 

 believe to be some new evidence, and ts extend 

 the scope of what appears to be an important 

 generalization. 



There are onlj- two clearly marked tj'pes of 



ova. These are, first, the holoblastic or evenly 

 segmenting, and, secondly, the meroblastic or 

 unevenljr segmenting. The so-called centro- 

 lecithal tj'pe 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 widelj' 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 segmenta- 

 tion, there can be but two forms of ova discrimi- 

 nated in the animal kingdom ; viz., those with, 

 and those without, a food-yelk. Those without 

 food-j^elk maj' be called homoplastic ; that is, 

 thej' are composed of but one kind of plasma, 

 all of which is germinal. The first segmenta- 

 tion-nucleus is central in position after fertili- 

 zation, 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 even- 

 sized spheres. The other type, opposed to 

 the foregoing, maj' be called the heteroplastic, 

 hj which it is intended to signify- that two or 

 more proteids maj' 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 cen- 

 tral position to a remarkable extent ; in fact, 

 it may be so displaced, as compared with its 

 position in very 3'oung 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 segmentation- 

 nucleus is not its original one, as an investiga- 

 tion 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 ger- 

 minative vesicle has migrated from the centre 

 of the ovum, towards the periphery, without 

 having suflfered anj^ marked change in size. 



To what cause is this permanent displace- 

 ment of the egg-nucleus due ? We find it to 

 occur only in those ova in which we maj' 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 maj' 

 be in the form of a clearly defined j'elk, or it 

 may make its presence manifest onlj' after the 

 beginning of segmentation, bj' aggregating at 

 one pole or cen trail}' as a less homogeneous, 

 more granular mass than the portion directl}" 

 involved in the process of segmentation. The 



