339 



to be the eleoblast, but more careful study shows an absence of the 

 spongy appearance characteristic of the eleoblast, and sections of the 

 organ show well developed sperm cells in its interior. In such a 

 section, the whole lumen of the testis is filled with the tails of the 

 sperm cells, and there is no doubt that the spermatozoa are mature 

 or nearly so. In the same individuals, sections through the "ovary'» 

 show that the egg has not yet begun to develop, and, since, in still 

 older stolons, no sign of segmentation of the egg appears, the eggs 

 in the younger stolons can not have been fertilized. Whether they 

 are ready for fertilization can not be told, except that the fact that 

 in considerably older stolons the eggs have not segmented would in- 

 dicate that the eggs at this earlier stage are not prepared for fertili- 

 zation. In much older free-swimming chains, the individuals of which 

 are about 8 mm long, I have found some cases in which the testis 

 has already disappeared, while the embryo is still in a very early 

 stage of development; none of the internal organs showing with any 

 distinctness in surface views. In S. cylindrica, then, the spermatozoa 

 ripen before the eggs. 



Correlated with this early ripening of the sperm, we see the 

 precocious development of the testis as figured. The testis is actually 

 no larger than it is in may species in which the sperm ripen late, 

 after the chain individuals have increased in size; but, iu proportion 

 to the size of the body, the testis of the young chain S. cylindrica 

 is much larger than in other species I have studied. This would 

 indicate that the observations of the early ripening of the eggs and 

 the delayed maturity of the spermatozoa in other species were correct, 

 and that S. cylindrica differs in this regard from most species. Study 

 of stolons of different ages from S. runcinata has convinced me that 

 in this species the relations are as usually described. In the older 

 stolons of this species, nearly ready to detach from the parent, the 

 testis does not yet appear, nor is it shown in younger stolons. 



In individuals from considerably younger stolons of S. cylindrica 

 I find the eleoblast slightly developed and appearing as figured by 

 Brooks 0- In the later stages, when the testis is well developed, 

 the eleoblast has disappeared, though in stolons of S. runcinata at a 

 corresponding stage of development it is still plainly seen. This early 



1) W. K. Brooks, The Genus Salpa. Memoirs from the Biological 

 Laboratory of the Johns Hopkins University, Vol. 2, 1893, Plate 8, 

 Fig. 2jc. 



