No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 375 



each " chromosome " consists of " two granules, at first of the 

 same size [which] grow v^ery unequally, so that one is often 

 considerably larger than the other. Hereupon some, but not 

 all, of these granules break down to form irregular strings of 

 minute karyomicrosomes which are distributed along the fibers 

 of the achromatic reticulum. . . . The large chromatin granules 

 which do not break down become the nucleoli of the pronuclei. 

 I am unable to state positively that in each Diplococcus-shaped 

 chromosome one of the granules breaks down to form a chain 

 of minute karyosomes while the other persists as a nucleolus, 

 but I am very strongly inclined to believe that this is the case." 

 These nucleoli are cast out into the cytoplasm when the first 

 cleavage spindle is formed, and there rapidly dissolve. Wheeler 

 accepts "Hacker's view of the secretory nature of the nucleo- 

 lus, at least so far as the germinal vesicle is concerned." 



Bancroft ('98), germinal vesicle of Distaplia: the nucleolus 

 "does not form the stellate body found in the old ova, as 

 Davidoff maintained, but is found within this body, which is 

 itself the remains of the germinal vesicle. The nucleolus at 

 this stage is quite complex, consisting of a homogeneous cortex, 

 an excentric finely granular medulla, and within the latter 

 several very highly refractive bodies, the largest of which may 

 have a granular appearance. During the greater part of the 

 growing period these refractive bodies are the only substance 

 in the germinal vesicle that takes the chromatin stain with a 

 methyl green and acid fuchsine combination." 



i8g8. 



Kostanecki ('98) confirms the observations of Wheeler ('95, 

 '97) in regard to the casting out of the nucleolus into the 

 cytoplasm, in the maturation of the ovum of Myzostoma. 



B. Botanical Literature. 



Schleiden ('38) is the discoverer of the nucleolus in plants, but 

 he gives it no name : " einen kleinen, sich scharf abgren- 

 zenden Korper, der, nach dem Schatten zu urtheilen, einen 



