HISTORY OF THE EGG FROM FERTILIZATION TO CLEAVAGE. 27 



inent is a passive one on the part of the nucleus '.' Allowing that the 

 spermatic body does not begin its centripetal march until after the ex- 

 trusion of the polar globules, as observed by Kultschitzky w in the egg of 

 .1 arts marginata, is that to be taken as an evidence that the cytoplasm 

 alone is responsible for the movement? Why are not the polar globules 

 carried to the centre of the blastodisc of the fish egg at the time they 

 are pushed beneath its surface? Obviously because they do not and can- 

 not enter into the same physiological relation that exists between nucleus 

 and cytoplasm. We do not know what this relation consists in, but there 

 is every reason to suppose that both factors sustain reciprocally active 

 relations. 



Now when we see the female pronucleus take the same position in the 

 unfertilized eggs of Li park dispar 26 that it takes in the fertilized egg of 

 this lepidopteron, we know that its migration can be accomplished with- 

 out the aid of the male pronucleus ; but there is absolutely nothing in 

 all this to indicate that the male pronucleus when present is without in- 

 fluence on the movement. Even where no evidence of such influence is 

 obtainable, we are justified in assuming it, since the most positive evi- 

 dence of its effects is furnished in certain eggs presenting conditions 

 favorable to demonstration. Take, for example, the direct observation of 

 Fol (No. 10, p. 106) on the egg of Asterias glacialis. "A mesure que Taster 

 male s'avance dans le vitellus, ses rayons deviennent toujours plus longs et 

 plus accentues; sa liaison avec son point d'origine a la surface du vitellus 

 se perd. Sa direction, d'abord eentripete, change, lorsque le pronucleus femelle 

 rioccupe pas le centre de Vceuf, pour se rapprocher de ce dernier noyau. En fin 

 le pronucleus femelle jusqu'alors immobile, se met en mouvement au mo- 

 ment ou il est atteint par les rayons de Taster male et la reunion des deux 

 noyaux s'opere promptement." 



Not less conclusive are the observations of Roux 26 on the Frog's egg. 

 The spermatic body takes at first a centripetal direction, penetrating to a 

 depth of 29-35 mm., and thus describing the "penetration path." By a more 

 or less abrupt curve the path then becomes directed towards the female 



24 N. Kultschitzky. Uebcr die Eireifung uud die Befruchtungsvoipiuge hei Ascaris marginaCa. Arch, 

 f. mikr. Anat., XXXII. •!. Deo., 1888. 



46 (J. Plainer. Die erste Entwickliing befruclitcter mid parthenogenctischer Eier von Liparis dixpar. 

 Biolog. Centralblatt, VIII. 17, Nov. 1, 1888, p. 522. 



26 Wilhelm Roux. Bcitnigc zur Entwickelungsmechanik des Embryo. Arch. I', mikr. Auat, XIX. 2, 

 1887. 



