126 JAMES O. FOLEV. 



gonial cells studied, points to the possibility of their being sex- 

 chromosomes, although no more positive evidence than this can 

 be presented at this time. If they are sex-chromosomes the 

 inference is that they would bring about the poultry type of 

 sex-linked inheritance in Umbra; in other words the male would 

 be of the two X, the female of the single X type. The condition 

 here seems to be much the same as that depicted by Agar ('i i), in 

 Lefndosiren; according to his figures 18 to 31 two large chromo- 

 somes almost identical as to size and shape can be followed 

 through the maturation division of the first spermatocyte, 

 although he does not indicate that they are sex-chromosomes. 



3. Multiplication. Multiplication takes place to a small extent 

 throughout the spermatogonial growth period. The new cells 

 produced by these divisions grow somewhat and probably take 

 part in the formation of some of the cysts within the lobule. 

 If the first divisions of the early migrant cells are considered as 

 the beginning of the multiplication period, then this period is a 

 prolonged one. About the middle of July, however, active 

 multiplication of the cells in some cysts is in progress. Such 

 multiplication in Umbra is very rapid, once the reorganization 

 of the lobules of the testis has taken place. Practically all of 

 the lobules have completed their reorganization by the beginning 

 of the first week of August. As before mentioned this reorgani/a- 

 tion of the lobules into cysts takes place not only through an 

 enlargement of the migrating cells but also to some extent 

 through their multiplication. Though isolated cysts in a lobule 

 may still show cells in the spermatogonial growth-phase, tin- 

 great majority of the cysts within any one lobule have practically 

 or entirely completed their multiplication and arc- ready for tin- 

 first maturation division by August. On the oilier hand a goodly 

 number of cysts within the lobule have, by that time, completed 

 the entire cycle of spermatogenesis. Turner ('19) says of tin- 

 perch, "As each spermatogonium gives rise to a group of de- 

 scendents they form a cyst and all pass through the same stages 

 of division at the same time"; and this is in tin- main also true of 

 It one considers a cyst in ['nihra as the product of a 

 single spermatogonium, then an estimate ol tin- number of 

 spermatogonial divisions which have occurred in any one cyst 



