EARLY DEVELOPMENT OF HYDRA. I I 



these cells frequently divided into two, three, four or even six 

 parts, usually all of unequal size. This process always took place 

 before the cutting out of the central nuclear-like portion. 



Brauer ('pirt, p. 170) makes mention of the " Dotterkernen, 

 der sogenannten Pseudozellen." In describing the growth of the 

 egg (p. 178) he speaks of "die Auflosung der Nahrzellen und 

 ihre Aufnahme als sogenannte Pseudozellen durch die Eizellen." 

 Further on in the same article (p. 184) he remarks that the struc- 

 ture of these bodies has been already described by Kleinenberg, 

 implying that his own observations agreed with those of the last 

 named author. In another paper of the same year ('91 (5') he 

 describes the origin of the pseudo-cells as follows : " Mit dem 

 Wachsthum der Eizelle . . . beginnt die Auflosung der Nahr- 

 zellen, indem die Umrisse unregelmassig werden und der Kern 

 verschwindet. Gleichzeitig treten auch die Pseudozellen als 

 kleine, von Anfangs an sich intensiv farbende Kugelchen auf, 

 welche rasch heranwachsen und die eigenthumliche Kernahn- 

 liche Form, wie Ciamician und Tichomirofif beschreiben, anneh- 

 men, sich aber von Kernen durch die starke Farbung besonders 

 der peripheren Partie unterscheiden lassen." He then states that 

 he agrees with Ciamician and Weisman as to their origin and 

 that they do not arise directly from nuclei as Tichomiroff had 

 shown, but that the latter author was deceived as to their true 

 nature by their nuclear-like appearance. 



Doflein ('97) describes in considerable detail the origin of the 

 pseudo-cells. He cites the views of several of the authors named 

 above, and then shows that in Tubiilaria larynx these structures 

 are the metamorphosed nuclei of the cells which have fused with 

 the ^gg and whose protoplasm has been added to it. These 

 nuclei in the earliest stage of their metamorphosis differ from the 

 nuclei of the primary germ cells only in that they lie in 

 vacuoles. Their further metamorphosis consists in the disappear- 

 ance of the vacuoles within the nucleolus, the thickening of the 

 peripheral zone of chromatin matter, and the gradual disappear- 

 ance of the clear non-staining area about the nucleolus. The 

 nucleolus then enlarges considerably and the change is complete. 

 By the use of a methyl-green-eosin stain he shows that a chemi- 

 cal change takes place in the nuclear substances during the meta- 



