286 BULLETIN OF THE 



satze erweiterten Bereiche, und zwar unter Verdrangung aller groberen 

 Kornchea aiis diesem Bereiche." In his opinion, the old nucleus suffers 

 complete morphological ruin. 



This method of increase of nuclei Auerbach designates as " palingenet- 

 ische Kernvermehrung," in opposition to that where no dissolution, but 

 a direct division, of the nucleus takes place. 



The central area of the stellate figures in the case of Liraax presents 

 objections to some of the views which Auerbach entertains. The fluidity 

 of the nuclear sap should reduce the refractive power of this portion of 

 the protoplasm ; as a matter of fact the refractive power increases toward 

 the centre of this area. The stellate centres are often at considerable 

 distance from the waning nuclear structure, and yet the side of the aster 

 toward the nucleus shows no differentiation corresponding to the sup- 

 posed flow of nuclear sap. I have every reason to believe, however, 

 that in Limax the central area of the stellate figure is, in the words of 

 Auerbach, "not a nucleus, also not the formative centre of a nucleus, 

 that it in fact does not even indicate the place at which the new nucleus 

 appears, and that the latter, even in its migration, does not advance into 

 [the centre of] the body of the sun." 



Lankester ('75, pp. 39, 40) asserts that, in the case of Cephalopods, 

 the cap of formative matter segregated to the smaller pole of the egg 

 " presents no nucleus, persistently, though a nucleus ma?/ appear in it 

 at the first." "I have most fully satisfied myself," he continues, "that 

 temporarily many of the segmentation products are devoid of nucleus." 

 The cells which result from the segmentation of the cap of formative 

 matter Lankester calls " klastoplasts." Before the superficial extension 

 of this cap of klastoplasts has begun, there appear in a deeper stratum 

 of the yolk pellucid nuclei, at first arranged in a circle around the cap. 

 These are called " autoplasts." They are of the same nature as the nu- 

 clei of cleavage segments. "I believe in the eggs of Loligo there may be, 

 according to season, an increase of these nuclei, or, on the other hand, 

 of these bodies, they being reciprocally vicarious within small limits." 

 No area becomes segmented around the autoplasts ; " they commence as 

 minute points, gradually increasing in size, like other free-formed nuclei." 

 In his preliminary account of the development of Pteropods, Fol 

 ('75, p. 196, also '75", p. 198) says that before each segmentation the nu- 

 cleus disappears, to be replaced by two moleculaV stars which arise in its 

 interior. The centre of each may be considered a centre of attraction : 

 all the vitelline substance yields to this attraction. After the cleavage 

 a nucleus reappears at the centre (au milieu) of each star. 



