CHAPTER VIII 



KEIMBAHN-DETERMINANTS AND THEIR SIG- 

 NIFICANCE 



It is customary to be suspicious of any peculiar 

 bodies revealed to us in fixed and stained material 

 under high magnification. There can be no doubt, 

 however, that most, if not all, of the cytoplasmic 

 inclusions mentioned in the preceding chapters are 

 realities and not artifacts. Some of them have been 

 seen in the living eggs ; most of them have been de- 

 scribed by several investigators; they occur after 

 being fixed and stained in many different solutions ; 

 and their presence is perfectly constant. The 

 genesis, localization, and fate of these bodies are 

 difficult to determine, and their significance is prob- 

 lematical ; but the writer has attempted in the follow- 

 ing pages to draw at least tentative conclusions from 

 the evidence available and to indicate what still 

 needs to be done. 



A. The Genesis of the Keimbahn-determinants 



The writers who have discussed the origin of the 

 keimbahn-determinants have derived them from 

 many different sources. In a few cases they are known 

 to be nuclear in origin, consisting of nucleolar or chro- 

 matic materials; they are considered differentiated 



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