THE MIGRATION OF THE GERM CELLS IN AMIURUS 



NEBULOSUS. 



FREDA M. BACHMANN. 



A study of the germ cells in Amiurus nebulosus was under- 

 taken with the hope of determining their origin, but because of 

 the difficulties in distinguishing them in the younger stages of 

 the embryo and the limited amount of time in which this work 

 was done, it was necessary to limit the subject to a study of 

 their number and migration after they are clearly distinguishable. 



The material was fixed in either Zenker's fluid or bichromate 

 acetic. The two fluids appear to give equally good results. All 

 sections were cuKjo microns thick and stained with Heidenhain's 

 iron-alum hematoxylin followed by Congo red or with Mayer's 

 hsemalum followed by Orange G. 



The origin and migration of the sex cells and the formation of 

 the germ gland in teleosts have been studied in a number of species 

 by several investigators. Some have concluded that the germ 

 cells are all or in part transformed epithelial cells ; others believe 

 they are never a part of the body tissues but are derived from 

 undifferentiated cells in the very early stages of development and 

 later migrate into the sex gland where by division, they give 

 rise to oogonia and spermatogonia. 



Nussbaum ('80) in working on the trout, found no evidence 

 of any epithelial cells transformed into germ cells. At a certain 

 stage in development, the germ cells divide and form little groups 

 or nests of cells. He thought these could not be transformed 

 epithelial cells because if the cells in the groups are of epithelial 

 origin, then why should they be in groups, and also, if epithelial 

 cells are continually being transformed into germ cells, then why, 

 when these smaller cells appear in groups, do the larger cells 

 which were in stages immediately preceding so suddenly and 

 completely disappear? Also he found if there was a large number 

 of cells in a nest the individual cells were smaller than those in 

 nests where there were but a few cells. He thought the size of 



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