THE SPERMATCK.I \lsis OF IMI!K\ I.IMI. 1 19 



are oval in shape tapering from the middle toward each end. 

 The testes do not fuse as they do in many fish but remain separate 

 throughout their entire length. It was found that material 

 from fish which were kept in the laboratory for more than a 

 week could not be relied upon, as it began to show abnormal 

 behavior. 



For cytological study material was fixed in Carney's, Gilson's 

 and Flemming's strong fluids, Flemming's modified according to 

 Hance ('17), and Bouin's fluid modified according to Allen ('16). 

 Allen's modification of Bouin's fluid was found to give the best 

 results, although Hance's modified Flemming gave fair fixation. 

 The testes \vere dissected out and quickly immersed in the 

 fixative, and then cut into very small pieces. The fixative was 

 kept at the same temperature as the water of the aquarium which 

 contained the fish. Safranin and gentian violet, or safranin 

 counterstained with licht-grun or iron-alum haematoxylin counter- 

 stained with eosin, acid fuchsin, picric acid, licht griin, or Congo 

 red were employed as stains. The best results with counter- 

 stains following Bouin's fixation were secured with solutions of 

 licht griin and Congo red in 95 per cent, alcohol. Sections were 

 cut from three to seven micra in thickness. Those of seven 

 micra w r ere best for studying the chromosomes and for making 

 chromosomal counts in the large spermatogonial cells. Smears 

 were also made but did not prove as valuable as the sections in 

 this study. 



SEASONAL CYCLE IN THE SPERMARY OF Umbra. 



The testes of Umbra are usually full of spermatozoa up to 

 the middle of May. Though there is some variation among 

 individuals and in different years on account of differences in 

 seasonal succession, expulsion of the spermatozoa usually occurs 

 during the last week or ten days of May. Following this there 

 is a period of rest in the testes until about the middle of July. 

 The primordial germ cells or primary spermatogonia, as I shall 

 designate them in this paper, are arranged around the periphery 

 of the lobule before and just following the expulsion of the 

 spermatozoa. This peripheral position of the primary sperma- 

 togonia in those lobules in w r hich a few spermatozoa remain, 



