588 BULLETIN OF THE 



■which marks the centre- of attraction ; it is the force set free in the act of fu- 

 sion, not the affinity of the already formed nucleus for other matter, which 

 induces the radiate appearance. If this view is justified, it seems to me that 

 it would not be necessary to make a specia,l case of Sagitta, and to hesitate, 

 as Fol does (p. 259), in comparing the structure which he there calls by the 

 non-committal name "la vacuole" with the male pronucleus of other animals.* 

 I have less hesitation in pronouncing this "vacuole" in every essential the 

 equivalent of the male pronucleus of other animals, as I have seen something 

 so nearly identical in Limax (see Fig. 68), where the staining of the structure 

 in question banishes all doubt as to its nuclear character. I must confess, 

 moreover, that I am considerably puzzled to know what Fol means by this 

 hesitancy, as I see no other possible explanation in view of the ultimate fate 

 of this vacuole. Instead of presenting any difference of primary, or even sec- 

 ondary importance, it seems to me a very welcome confirmation of the substan- 

 tial identity of the astral phenomena which accompany the male pronucleus 

 and those which preside at the subsequent segmentations.! 



In regard to the nature of the rays, the author says, the hypothesis of a 

 simple polar attraction which arranges the vitelline granulations in a certain 

 order without displacing them is not defensible ; for these bands are in all 

 cases broader than the mean distance of the lecithic granules. These fila- 

 ments, so distinct in acetic acid, do not admit the belief in a simple polari- 

 zation of molecules. The accumulation of clear protoplasm around the nucleus 

 and its poles could not take place without currents of this viscid substance. 

 But if there are currents, in what direction are they produced ? In the sea- 

 urchin, before the formation of the amphiaster, the perinuclear mass moves 

 toward the equator, and becomes a disk at the moment when the pinnate 

 arrangement of the clear streaks becomes visible. Here it may well be that 

 the currents arising in the equatorial region proceed beyond the poles to spread 

 their substance in the vitellus. During the division of the amphiaster the 

 facts appear to favor the supposition of centripetal currents.. The centripetal 

 movement of the thickenings [in the unipolar rays] which are rendered visible 

 by acetic acid, and the continuous growth of the central masses, appear to indi- 

 cate a slow advance of the sarcode toward the centre of the aster. 



Nevertheless, observations on other objects must, he says, be taken into the 

 account. Auerbach's theory of a dispersion of nuclear fluid is untenable, since 

 the asters are formed before the volume of the nucleus is diminished. On the 

 other hand, Flemming has seen pseudopodia at the surface of the polar globule 

 in Anodonta, of which the following explanation is offered. From the figures 



* "Chez Sagitta, par exernple, nous avons vu que Taster traine a sa suite una 

 sorte de vacuole toujours croissante ; le centre de Taster se trouve au herd allonge de 

 cette vacuole, toujours du cote vers lequel elle se dirige. C'est done dans Taster et 

 dans son centre que reside la force motrice, tandis' que la vacuole, que j'hesite du 

 reste k comparer au pronucleus des autres animaux, est trainee k sa suite." 



t P. S. — May it not he that this is a typographical error, and that the negative 

 has been inadvertently omitted ? 



