MUSEUM OF COMPARATIVE ZOOLOGY. 477 



not so many individual nuclei, but that they furnish the material for the 

 construction of a nucleus. 



A comparison with the conjugation of Infusoria leads Biitschli to the 

 conviction that in the fecundation of the egg similar modifications — 

 " total or partial renewal of the nucleus, or a material revival of the 

 same by the importation of a new part" — may be encountered (p. 438). 

 The two nuclei (pronuclei) are alike, and arise in the same manner. 

 There is nt>t the least justification for interpreting them as egg nucleus 

 and sperm nucleus in 0. Hertwig's sense. The existence of a multiple 

 of nuclei is a phenomenon induced by the antecedent subdivision of the 

 nucleus of a spermatozoon which penetrated the yolk, not by the pene- 

 tration of several spermatozoa, as 0. Hertwig concludes. 



To ascertain whether the formation of polar globules is dependent on 

 fecundation the author instituted experiments on two nematodes (Rhab- 

 ditis teres and R. pellio) rearing isolated females. The eggs never 

 produced polar globules, and no changes of any sort overtook the germi- 

 native vesicle or dot until the yolk began to show signs of degeneration. 

 Biitschli concludes (p. 442) that both views are warranted, — that in one 

 case it is in consequence of, and in another independent of, fecundation, 

 but it is not a phenomenon of the maturation of the egg ; it is one of the 

 first of the phenomena of development, which in certain cases may take 

 place parthenogenetically before fecundation. 



Strasburger (76, pp. 21, 295, Taf. II. Figs. 19-23, Taf. VII. Figs. 

 9-11) has given the following account of fecundation in Picea vulgaris 

 after the formation of a canal cell which remains in close contact with 

 the ovum. The pollen tube, making its way through the disorganized 

 cells of the neck of the archegonium, destroys the canal cell and reaches 

 the ovum, where its previously dissolved contents pass by a diosmotic pro- 

 cess through its very porous tip into the interior of the ovum, and are 

 taken up by the nucleus of the latter. This may take place in a con- 

 tinuous manner, or the contents may first be accumulated in a nucleus- 

 like structure at [i. e. outside] the end of the pollen tube, and then 

 advance to the •' Eikern," or finally several such nuclear structures may 

 arise at the pollen tube and be successively received by the Eikern. 

 The latter, thus fecundated, Strasburger calls the germ nucleus, Keim- 

 kern ; it soon begins to disappear by a radial distribution of its mass in 

 the plasm of the egg. 



His studies (p. 306) on the fecundation of animal eggs were made 

 upon Phallusia mammillata. In the first edition of this book Stras- 

 burger held that the " Keimkern " (segmentation nucleus) took its 



