704 THE AMERICAN NATURALIST. [VoL. XXXIX. 



bearing of these studies. An admirable review of the early lit- 

 erature is presented in Wager's paper of 1898. 



Wager ('98) himself has made one of the most detailed studies 

 of the yeast cell and his conclusions on the presence of a 

 " nuclear apparatus " will be made the starting point of our dis- 

 cussion. The yeast cell contains a structure, termed by Wager 

 a " nuclear body," generally situated at one side, close to the 

 cell wall. This body resembles the nucleolus of higher plants in 

 its homogeneous structure and reaction to stains. Besides the 

 " nuclear body " Wager finds a vacuole always present which 

 contains granular material and is an important part of the nuclear 

 apparatus. This " nuclear vacuole-" must be carefully distin- 

 guished from other vacuoles of the usual type which merely con- 

 tain glycogen. There are besides some globular bodies in the 

 protoplasm whose nature may be oil in some cases and proteid in 

 others. The "nuclear body" is always in close contact with the 

 " nuclear vacuole " but is never within it. The amount of granu- 

 lar material in the nuclear vacuole is variable but it sometimes 

 contains a dense mass. This content is believed to be chroma- 

 tin from the behavior to stains and insolubility in digestive 

 fluids. Sometimes the nuclear vacuole disappears but in such 

 cases the granular network is found in contact with the nuclear 

 body and sometimes distributed about it in a very regular man- 

 ner. The chromatic granular material appears then to be a per- 

 manent substance in the cell and always closely associated with 

 the nuclear body, sometimes distributed about it and sometimes 

 included within a special vacuole. 



Wager concludes that the nuclear apparatus consists of (i) a 

 nucleolus (nuclear body) and (2) a store of chromatin in a net- 

 work, either enclosed in a vacuole in close contact with the 

 nucleolus or lying freely about the nucleolus or sometimes 

 disseminated in granules generally throughout the cytoplasm. 

 Wager believes that the nuclear vacuole arises from the fusion 

 of numerous small vacuoles which lie around the chromatin gran- 

 ules which thus come to lie within a common vesicle. This 

 mode of origin seems reasonable from what we know of the 

 history of the nuclear vacuole which arises around the chromo- 

 somes that gather at anaphase of mitosis to form daughter 



