28 



C. ISHIKAWA. 



of Heriwig upon Ascaris by giving different interpretations to the results 

 obtained by the latter investigator. AMiatever may be the interpretation 

 in the case of Ascaris, my own case, given above, can not to my 

 mind be made to coincide with his observation on Pyrrhocoris, I will 

 not, however, assert the " Keduktionstheilung " in the formation of 

 the second polar body and in the last cell division in the spermatogenesis 

 to be the universal rule until a sufiicient number of observations be 

 obtained in other groups of animals and perhaps of plants too. 

 Theoretical considerations concerning the phenomena of fertilization 

 lead us in all probalDility to the " Keduktionstheilung " as occurring 

 in the second polar body and in the last division of spermatic cells. 



I will now consider very shortly the phenomena of fertilization. 

 As stated above, tlie maternal and paternal nuclei do not unite into a 

 single segmentation nucleus, as Hertiüig^^~^ for the tirst time gives 

 out, but remain separate from each otlier till after the complete forma- 

 tion of the segmentation spindle. Something of the kind had been 

 already observed l^y \arious ^vritery, Ijut this fact was brought out in 

 its full light only by the last work of Ed. ran Bencden and Jul in *^-' 

 on Ascaris. In the eggs of a, c(jpepod Crustacea (Cetocliilus) Grohben-^' 

 observed for tlie -first time, that the two nuclei do not become united 

 with one another and form a single segmentation luicleus, but 

 " stossen die Ijeiden Kerne, Eikern und Spermakern, aneinander und 

 sind nur noch durch eine zarte Wand voneinander geschieden. Auf 

 dieses Stadium folgt sogleich die Bildung der ersten Kernspindel." 

 But above all, the recent valuable investigations of B over i^^^ on this 

 head in various groups of animals, as well as his enumeration of 

 facts obtained by previous workers, make us accept this as the rule, 

 and the perfect union of both the nuclei as exceptional cases only. To 

 these we may add the observations of Henliincf^^^ on the eggs of Fieris, 

 as well as that of Hmcher''''^on Cijclops. My own observation on the 



