No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 28 



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germinal vesicles of various animals. In Eiicope polystyla there 

 is one nucleolus in small eggs, several in riper ones : " Es 

 Hess sich hier feststellen, dass die zahlreichen Nucleoli durch 

 Ablosung vom urspriinglichen einfachen Keimfleck entstehen." 



Klein ('78) studied the stomach cells of the newt, and con- 

 cludes " that in most cells the so-called nucleoli are local 

 accumulations of the intranuclear network, that they are incon- 

 stant in size and number, and that they are only transitory 

 appearances." 



Schindler ('78), Malpighian tubules of insects : after a cell 

 has become obliterated by the outflow of its secretion, its 

 nucleus becomes a new cell, and its nucleolus a new nucleus. 



Whitman ('78) found in the ^^^ of Clcpsme one to three 

 nucleoli, each '* composed of several highly refractive pieces." 



Bergh ('79) found in the ^^^ of Gonothyraea {Campamilaria) 

 a single large nucleolus, which is usually ro.und, but sometimes 

 with irregular outlines caused by slow amoeboid movements 

 (observed in life), these motions being most vigorous later, 

 when the nucleolus begins to divide. It increases in size, and 

 acquires one or two vacuoles. In a later stage, but before the 

 production of the pole bodies, there are a number of irregular 

 nuclear bodies (staining as the original nucleolus), which had 

 been produced by division of the nucleolus ; in one case he 

 actually observed the division of the nucleolus, which lasted 

 half an hour, and at the same time the vacuole of the primitive 

 nucleolus seemed to divide into two, so that each daughter- 

 nucleolus received a daughter-vacuole. " Oft macht es den 

 Eindruck, als ob das Volum der secundaren Keimflecke zusam- 

 mengenommen grosser ware, als das der primaren fur sich 

 . . . eine active Wanderung der Nucleoli durch den Kernsaft, 

 wie dies Auerbach ['74] bei gewissen Nematoden in den Vor- 

 kernen gesehen hat, kommt wahrscheinlich hier nicht vor." 

 The nucleolus also divides in the t%^ of Clava. In the eggs 

 of PsantinccJiimis and EcJiiiwcardium, the single nucleolus 

 begins to fragment before the chromatic network has disap- 

 peared. The Phallusia egg contains one large germinal 

 spot, which probably disappears without fragmenting : " ich 

 habe namlich unter Eiern, die im Keimblaschen einen scharf 



