No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 325 



does not become a " Nebenkern " (in opposition to the views 

 of Ogata). In the eggs of Rana and Nectiiriis the chromatin is 

 " principally collected in the form of nucleoli at the periphery," 

 but it is also contained in certain threads in the nucleus. He 

 concludes from the study of the reactions of the substances 

 to the indigo-carmine stain: "the peripheral nucleoli generate 

 a substance, therefore, which diffuses gradually through the 

 nucleus, then into the cell protoplasm, the point in time of the 

 latter occurrence corresponding with the formation of the yolk 

 spherules. The mode of origin is through a process of deposi- 

 tion from the nucleus of a substance allied to chromatin in the 

 cytoplasm. ... I regard the yolk spherules as formed by the 

 union of a derivative of the nuclear chromatin with a constituent 

 of the cell protoplasm." 



C. Schneider ('91) concludes that the true spherical nucleoli 

 " ebenso wie die Klumpen [of the chromatic network] aus 

 [achromatischen] Geriist und Chromatin bestehen und die 

 Unterschiede beider nur morphologischer Natur sind." In the 

 testicle cells of Astacns the nucleoli are spherical, with " eine 

 deutliche Membran an und durch welche genau wie bei der 

 Kernmembran [achromatische] Geriistfaden treten. . . . Der 

 ganze Unterschied zwischen Nucleolus und Klumpen besteht 

 also hier darin, dass um ersteren die Fasern zu einer Membran 

 sich zusammenlegen . . . was man ringformig am Rande des 

 Nucleolus wahrnimmt, ist sicher nicht die optische Wiedergabe 

 einer Membran, sondern durch das Brechungsvermogen der 

 Wandung des Nucleolus veranlasst." The nucleolus in eggs of 

 Echinoderniata is homogeneous only in the final stages of its 

 formation. Nucleoli are only metamorphosed portions of the 

 true chromatin, and represent reserve masses of this substance : 

 " die Zusammenballung kann nur eine Befreiung der chroma- 

 tischen Substanz von ihrer Arbeitsleistung bedeuten." 



Wolters ('91) studied the sporulation of Monocystis : in the 

 youngest individuals there is one nucleolus, which "in seinem 

 Innern sich starker tingirende chromatische Kugein fiihrt." In 

 larger individuals the nucleolus consists of eight spheres, " Diese 

 Kugein ftihren in ihrem Innern wieder Stabchen und Korner." 

 Just before the conjugation of two individuals this compound 



