256 



cussing the origin of the ectomesoblast from three quadrants in Crepi- 

 dula says, — "it is probable that the radial origin of mesoblast is to 

 be considered a primitive character; its bilateral origin, a secondary 

 one. In other words, the larval mesoblast is the more ancestral, and 

 it might properly be called the primary or radial mesoblast, 

 while that formed from 4id might be known as secondary or bila- 

 teral mesoblast". These suggestions are made all the more pro- 

 bable by the fact that some of the mesenchyme cells in Thalassema 

 are rudimentary and possible cases of ancestral reminiscence. 



This is, as far as I know, the first case in which both the origin 

 and fate of completely rudimentary cells has been definitely determined 

 in cell lineage, although such cells have been described tentatively in 

 several other cases. Without discussing these cases here I will only 

 point out that the behavior of the rudimentary cells in Thalassema 

 brings forcibly to mind that of the pajdomesoblast cells in Capitella, 

 described by Eisig as wandering through the endodermal mass and 

 finally emerging as functional mesenchyme cells. There is, however, 

 no doubt of their final absorption in Thalassema. It is difficult to 

 avoid the conclusion that they may have been functional at some ear- 

 lier time, but have now become wholly degenerate. 



Zoological Laboratory, Columbia university, January 1902. 

 (Eingegangen am 15. Februar.) 



Nachdruck verboten. 



Die Reifung der parthenogenetischen Eier von Artemia salina. 



Von Dr. Alexander Petrunkewitsch. 



(Aus dem Zoologischen Institut der Universität Freiburg i. B.) 



Mit 4 Abbildungen. 



Das kleine Salzwasserkrebschen Artemia salina vermehrt sich 

 bekanntlich durch parthenogenetische Dauereier, die von einer sehr 

 dicken Chorionhaut umgeben sind, ebenfalls parthenogenetische Subitan- 

 eier, welche sich im Uterus des Muttertieres bis zum Naupliusstadium 

 entwickeln, und endlich auch durch befruchtete Eier. Die Männchen 

 kommen bei Odessa noch ziemlich häufig vor, dagegen sind sie bei 

 Marseille und Triest äußerst selten zu finden. Hier sind also diese 

 Phyllopoden auf parthenogenetische Fortpflanzung angewiesen. Um so 

 sicherer ist man bei der Untersuchung, daß man nur mit unbefruchteten 

 Eiern zu thun hat. 



