No. 2.] OOKINESIS. 237 



friiher der Samenfaden das Ei aufgesucht hat, so wandert jetzt 

 der Spermakern in get'ader RicJitung dem Eikern entgegen, 

 welcher sich gleichfalls, wenn auch vicl langsainer^ in Bewe- 

 gung setzt." F'ol (6, p. 259) puts it thus: "Ainsi lorsque le 

 noyau femelle se trouve dans une position excentrique ct que le 

 noyau male prend naissance pres de ce dernier, il marche directe- 

 ment a sa rencontre suivant tme corde de cercle au lieu de se 

 rendre d'abord au centre du vitellus." 



These descriptions would be strictly accurate if our two 

 forces acted consecutively and not concomitantly; i.e , if nuclear 

 attraction acted alone before the meeting of the pronuclei, and 

 centripetal attraction alone after this event. It is possible — 

 and this observation of Fol makes it highly probable — that 

 the attraction between the pronuclei is much stronger than the 

 centripetal attraction. We know of no fact that forbids this 

 supposition, and, if this point be conceded, the difficulty of recon- 

 ciling the observation with our views practically disappears. 



That what we have called centripetal attraction is a recipro- 

 cal action between ooplasm and pronuclei is a conclusion 

 supported by still another interesting fact. In the centrifugal 

 march of the germinal vesicle and in the maintenance of a pe- 

 ripheral position by the archiamphiaster during the production 

 of the polar globules, there is satisfactory evidence, as Fol 

 has already pointed out, of a repellent action. In those cases 

 where the spermatozoon penetrates the ovum before the elimi- 

 nation of polar globules (Teleostei, Nematoidea, Hirudinea, 

 etc.), we have attraction and repulsion exhibited at one and the 

 same time, and the ooplasm is the common factor in both 

 actions. It is thus made evident, first, that the body attracted 

 and the body repelled cannot be identical in molecular con- 

 stitution ; and second, that the two modes of action are due to 

 the unlike physico-chemical relations which these bodies respec- 

 tively sustain towards the ooplasm. 



Allowing that both the attraction and the repulsion represent 

 reciprocal action, we are brought face to face with the question 

 of the relative importance of the two factors engaged in each 

 case. Do the points just noticed throw any light on this 

 question? I believe they furnish at least one very important 

 evidence in support of the opinion that the nucleus takes the 

 initiative in action. 



