MUSEUM OF COMPARATIVE ZOOLOGY. 419 



face, and is strikingly similar to the veil-like layer seen by Oellacher 

 in the unimpregnated egg of the trout. Van Bambeke, however, objects 

 to Oellacher's interpretation of this layer, as far at least as regards 

 batrachians, since in the eggs of the latter the envelope of the germina- 

 tive vesicle never presents the characters pointed out by Oellacher for 

 the trout's egg. 



Greeff C76, pp. 34, 35) gives a short preliminary notice of early 

 stages of Asteracanthion rubens. The mature egg has two envelopes : 

 ** Gallertzone " and " Eihaut." The yolk is composed of a homogeneous 

 clear " Grundsubstanz " and two kinds of granules. The germinative 

 vesicle is clear, and has a distinct membrane ; the germinative dot is 

 more compact, and embraces small round vesicles variable in number 

 and size. Delicate filaments, stretched through the space of the vesicle, 

 are beset with pearl-like nodules, and exhibit spontaneous motion and 

 branching. After fructification — or without it, if the egg remains a 

 time in pure sea-water — the vesicle disappears, but the germinative dot 

 persists. This, in the fecundated egg, migrates like an amoeba through the 

 yolk. The latter assumes a radial appearance about the now centrally 

 located germinative dot. The polar globule appears with the first-seg^ 

 mentation constriction, or even later. (!) Nothing of a spermatic nucleus 

 was seen, nor are the polar globules to be connected with spermatozoa. 



GiARD ('76", pp. 233, 234) traces early changes in the egg of one of 

 the sedentary annelids (Salmacina Dysteri) as follows. After fecunda- 

 tion the germinative vesicle ceases to be visible, and one observes the 

 appearance of a circular, finely granular spot at the surface of the egg, 

 over against which there are two polar globules. The spot in turn dis- 

 appears and the egg suiFers a constriction less (f) pronounced on the side 

 where the spot was situated. 



Besides the entire absence of the germinative vesicle in the excluded 

 eggs of the spider (Philodromus), Ludwig ('76, pp. 473, 479) contrib- 

 utes nothing which concerns us in this connection. 



Stecker ('76^ p. 125) also reports for the eggs of Chthonius that the 

 germinative vesicle — after becoming more elongated, as seen in his 

 figures — entirely disappears, and near the place where it perishes a 

 brown roimd spot, composed of the " coarser granules " of the proto- 

 plasm, makes its appearance. This undergoes division with the subse- 

 quent total segmentation of the egg. 



In a chapter first introduced into the second edition of his book on 

 " Zellbildung," etc., Strasburger ('76, pp. 297-305, Taf. VII., VIII.) 

 discusses at some length the question of the fate of the germinative 



