MUSEUM OF COMPARATIVE ZOOLOGY. 247 



(Keimzellen) and daughter cells, from which the male elements of reproduction 

 are developed in Nematodes. In Ascaris mystax, A. marginata, A. megalo- 

 cephala, and A. depressa, the same phenomena were observed. After the dis- 

 appearance of the nucleus of the parent cell, the granules retreat a little from 

 tlie cell wall, and begin gradually to assume a very uniform radial arrangement, 

 like acicular crystals emerging from a somewhat clearer common centre. There 

 is no nucleus in this centre, but the granules there are fine. (This whole 

 granular portion Meissner erroneously considered to be the nucleus, Kernmasse.) 

 The centre of radiation, hitherto single, becomes indistinct, and gradually a 

 (hjuble or multiple arrangement makes its appearance, while the nucleus be- 

 comes constricted. The centre of radiation moves continuously toward, and 

 finally attains, the centre of the new nuclei (Kernmassen), which furnish the 

 basis for the formation of the corresponding cells. 



The passage in Remak ('55, p. 132) cited by Whitman ('78", p. 16) as evi- 

 dence of the former's observation of a radial arrangement of the yolk substance 

 in the segmenting eggs of Rana, does not seem to me as convincing as one 

 might wish. That Remak himself had no such conception of the nature of the 

 appearances figured (Taf, IX. Fig. 2, op. cit.) must, I think, be tolerably 

 evident from the context.* The passage (compare Taf. IX. Fig. 2 of Remak's 

 work) in question (§ 10, p. 132) is as follows : " Legt man die Halften des 

 Eies in diesem Zustande [i. e. during the first segmentation] aus einander, so 

 erkennt man an beiden durchaus gleiche Beschaffenheit der Innenflachen : 

 zunachst eine centrale runde oder ovale Bruchflache von kornigem Gefiige und 

 von wechselendem Umfange, so zwar, dass sie den grossten bis herab zum 

 kleinsten Theil der Innenflache einnehmen kann. Die scharfe Grenze der 

 Bruchflache wird durch den Uebergangsrand der beiden Scheidewande gebildet: 

 sie macht sich durch die Glatte und Farbung der letzteren leicht kenntlich. 

 Im Bereiche der unteren Eihalfte sind die Scheidewande durchaus weiss oder 

 weissgelblich, also in ihrer Farbe nur wenig von dem angrenzenden Zooplasma 

 (Dotter) verschieden, dagegen nehmen sie am Aequator allmalig eine schmutzig- 

 graue oder schwarzliche Farbung an. Namentlich sieht man haufig dunkele 

 Streifen in radialer Richtung von dem schwarzen ausseren Rande der Be- 

 riihrungsflache, der zugleich die Grenze des freien Theils der Eizellenmembran 

 bildet, bis zum Rande der Bruchflache sich hinziehen, was die Vorstellung von 

 einem lebhaften centripetalen Zuge erwekt, mit welchem die Scheidewande der 

 Abschniirung zustreben." It would appear from this, I think, that Remak 

 located this phenomenon in the " Scheidewande " rather than elsewhere, and 



* As is well known, Remak distinguished between what he calls " Einfurchung" 

 and "Durchfurchung." The former is accomplished by an annular furrow, which 

 advances only a certain distance toward the centre of the egg, and is accompanied by 

 the involution of the "egg-cell membrane." From the floor of the furrow thus 

 formed there proceeds, without (direct) participation on the part of the "egg-cell 

 membrane," the formation of a new structure, — partition walls (Scheidewande), — 

 which completes the separation of the halves of the segmenting egg. This last sup- 

 plementary act is consequently called DurcMnrchnng. 



