154 Robert Müller: 



suchungen wurden an Alcyonium digitatum fortgesetzt von H i 1 P). 

 Dieser hatte mit erheblichen Schwierigkeiten zai kämpfen namentlich 

 bei der künstlichen Befruchtung der Eier, aber auch bei deren 

 histologischen Untersuchung, und er macht das Zugeständnis: „In 

 fact for cytological studies the egg of Alcyonium proved a most 

 unfavourable object", ein Satz, der leider für die Eier sämtlicher 

 Alcyonaceen und für deren gesamte Entwicklungsgeschichte gilt. 



Hill gibt nun folgende Darstellung der Reifeteilungen: „The 

 changes that now take place, are quite unlike any that have hitherto 

 been figured or described. Instead of the nuclear membrane dis- 

 solving and two mitoses taking place without an intermediary resting 

 stage, nothing of the kiud happens. Of this fact I feel convinced. 

 Of the large number of eggs examined I have never seen the smallest 

 trace of anything that can be called „polar body". Of what actually 

 does take place there of I am not equelly sure, but if I Interpret 

 my preparations correctly it is somewhat as follows: The lump of 

 chromatin divides into halves amitotically. The nucleus becomes 

 constricted into two, though there is no vestige of spindle or centro- 

 some. A slight modification and absence of yolk in the protoplasm 

 surrounding the nucleus may represent a niodified archoplasm. 

 I have never discovered the least trace of a radiate protoplasmatic 

 Strand. One of the halves thus formed remains unaltered except 

 that the round chromatin mass breaks up into small bits, which 

 soon dissolve or at least no longer take the stain. The nuclear 

 membrane is not reformed. The remaining half divides again in 

 the same way and almost immediately disappears. The chromatin 

 seems to be rapidly disintegrated becoming a faintly staining granulär 

 mass and than all trace of this half of the original nucleus is lost. 

 The other moiety is longer lived and may be now called the female 

 pronucleus. It comes to lie on the extreme periphery of the cell, 

 almost suggesting that it will be thrown out, but its fate is otherwise. 

 I gradually dwindles to the smallest hollow vesicle just discernible 

 and than disappears leaving no trace of its presence. The deeply 

 staining yolkless protoplasm, referred to as beeing possibly a modified 

 archoplasm, also vanishes. The egg is now without any nucleus 

 and in this State leaves the polyp." 



1) Hill, Notes on the maturation of the ovum of Alcyonium digitatum. 

 Quart, journ. of microsc. science vol. 39 p. 493 — 505. 



