474 BULLETIN OF THE 



83, and '76^ pp. 178- 182) paper* on the germinal vesicle and the first 

 embryonic nucleus, for it is an attempt to harmonize Hertwig's observa- 

 tions on Toxopneustes with the author's own studies on mammals, which 

 was only made possible, as Hertwig ('77, p. 77) himself has very clearly 

 shown, by a misconception of the account given by the latter. Van 

 Benedcn's assumption that Hertwig's *' Spermakern " is a nucleolus finds 

 no support in Hertwig's description, and the protoplasmic area surround- 

 ing it is certainly not a nucleus, and therefore not comparable with Van 

 Beneden's ^pronucleus pcripherique." While there is no reason to 

 question the interpretation which Van Beneden assigns to his own ob- 

 servations, his attempts to subject Hertwig's observations to an unnatu- 

 ral alliance with his own must be regarded as unsuccessful. 



In the Qgg of the common toad after fertilization Van Bambeke ('76, 

 pp. 117- 135, PI. II.) has observed that meridional sections exhibit, in- 

 stead of a single pigmented trail, — the claviforrn body of the unfertil- 

 ized egg, — two such trails. One of these, the "trainee en boudin," is 

 slightly swollen at its internal end, and reaches nearer to the centre of 

 the yolk than the second, — " trainee triangulaire," — about the inner 

 end of which it is curved as about a centre. At its periphery it abuts 

 upon the germinative fossa. This the author thinks is unquestionably 

 the claviforrn figure of the unfertilized egg made to take a curved course 

 by the pushing in against it of the second or triangular trail. The latter 

 is also mingled at its base with the pigmented cortical layer of the supe- 

 rior half of the e^g ; its apex is directed inward, and is slightly curved 

 upward so as to terminate in the space surrounded by the curved " trainee 

 en boudin." In the terminal part of the triangular trail was once seen 

 a clear homogeneous point limited by a strongly pigmented contour, 

 which the author considers the nucleus of the first segmentation sphere. 



Similar conditions are found in fertilized eggs of Pelobates. Here, 

 however, the claviforrn figure is not curved, and its inferior enlargement, 

 in place of being a pigmented mass, is less deeply colored than the zone 

 which immediately surrounds it. The apex of the triangular trail, hav- 

 ing come to occupy the centre of this enlargement, is seen to abut upon 

 an elliptical nuclear mass (nucleus of first segmentation sphere), which 

 is a little clearer than the surrounding yolk, and is limited by a pig- 

 mented contour, whence granular striations of the yolk radiate. 



Observations of a similar kind on the eggs of the Axolotl convince the 



* The EngUsh translation of this paper ('76^) exhibits an omission which is of 

 rather vital importance to Van Beneden's argument. It may be corrected by insert- 

 ing, in the 15th line from the top of p. 181, " nuclei of the " before '* cleavage spheres." 



