460 ROBERT W. HEGNER 



A body stained deeply by nuclear dyes which was found by O. 

 Van der Stricht ('09) in the bat at the time of the first cleavage 

 mitosis, may be similar to the 'corps enigmatique' of the cat. 

 It is also worth recording that Jorgensen ('10) finds that the 

 oogonium of the sponge at the earliest stage when it can be 

 recognized, contains a granular body not present in the somatic 

 cells (fig. 23, F). 



6. THE GENESIS, LOCALIZATION, DISTRIBUTION AND FATE OF THE 

 KEIMBAHN-DETERMINANTS 



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 cyto- 

 plasmic inclusions mentioned in this paper are realities and not 

 artifacts. Some of them have been seen in the living eggs; most 

 of them have been described 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 signif- 

 icance is problematical; but the writer has attempted in the fol- 

 lowing pages to draw at least tentative conclusions from the evi- 

 dence 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 chromatic materials; they are considered differ- 

 entiated parts of the cytoplasm by some investigators; in some 

 species they are extra-cellular bodies, such as nurse cells. 



Table 1 indicates the number and diversity of the animals 

 in which Keimbahn-determinants have been described, and 

 shows the increasing interest given to this subject within recent 

 years, over half of the papers listed having been published since 

 1908. Several cases have been referred to in the text, but 

 omitted from the table because of insufficient evidence regarding 



