MUSEUM OF COMPARATIVE ZOOLOGY. 475 



♦ 

 author that the triangular trail of the tailless Batrachia is homologous 



with that which takes its origin from the "trous vitellins," as previously 

 described by him ('70, pp. 64, 65). Finally, after a review of the liter- 

 ature, Van Bambeke arrives at the conclusion that the eggs of the 

 Batrachia, immediately after impregnation, still embrace traces of the 

 claviform figure, but nothing discloses the presence of the " Eikern " of 

 Hertwig, or the "pronucleus central " of Van Beneden. The nucleus of 

 the first segmentation sphere arises from the periphery ; it very probably 

 results from the penetration into the vitellus of a spermatozoon, which 

 leaves as a trace of its passage the " trou vitellins " and the " trainee 

 pigmentaire." 



In Nephelis, after the conversion of the germinative vesicle into a 

 nuclear spindle, Bijtschli ('76, pp. 216, 217) has seen a little elevation 

 of clear protoplasm near the animal pole of the yolk, and believes it is 

 caused by the union of a spermatozoon with the yolk, during which the 

 spermatozoon, possibly by swelling, has become metamorphosed into the 

 protuberance. 



Other phenomena, which Butschli did not think of connecting with 

 fecundation, are probably phases of that process. The " third " system 

 of rays about a homogeneous area we may now safely infer to be the 

 male aster. The relation which the nucleus (male pronucleus) sustains 

 to this " area " deserves attention. According to the text, " it always lies 

 nearly in the periphery of the central area." From Fig. 3, Taf I., it is 

 evident that it lies in that part of the periphery nearest the female pro- 

 nucleus. I do not know of any other observation which agrees with 

 this in the particular last mentioned. In eggs of Cucullanus that 

 have passed the seminal receptacle (p. 223), a clear corpuscle, which en- 

 closes a cluster of granules, is found imbedded in the surface of the yolk. 

 It is, says the author, the result of the union of a spermatozoon with the 

 yolk (see Taf III. Figs. 1, 7, 12). It, however, disappears before the 

 beginning of the formation of new nuclei. The latter arise close under 

 the surface of the yolk, and are from the beginning distinctly vesicular, 

 with dark envelope and granular contents, but never acquire a special 

 nucleolus. They migrate toward the centre and become fused into a 

 single nucleus. In Anguillula rigida (pp. 232, 233) the Qg^ unites with 

 the first spermatozoon with which it comes in contact, but never with a 

 second. 



In the mollusks studied (p. 238) the first evidence of the existence of 

 a male aster was observed (Lymnseus) when the first polar globule had 

 been eliminated. It already occupied the centre of the yolk. A nucleus 



