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566 Bashford Dean hiemorial Volume 



reproductive organs and those having only one side functional as in Dasyatis say now to be 

 briefly considered. 



Dasyatis say. — The common stingray or "stingaree" also abounds at Beaufort, and in 

 1912 I reported the results of my dissections over a number of years. Sixteen non-breeding 

 females (uteri showing no signs of having eggs in them) ranging from 13 to 35 in. in width 

 had the left ovary from two to three times the size of the right. Thirteen breeding females 

 (13 to 35 in. wide) had the left ovary functional (with eggs 12-18 mm. in diameter) and 

 the left uterus greatly dilated — some with embryos, and some awaiting the coming of eggs. 

 In the course of several summers' work, no right ovary was found with any eggs in it 

 and no right uterus was ever functional. These facts were paralleled by my studies of 

 another species of the same genus. 



Dasyatis hastata. — This is the common stingray of southern Florida. At Key West 

 and at Tortugas, I dissected 10 specimens. Five were adults ranging from 3 to 4.5 ft. 

 wide. In these, the left uterus only was enlarged and functional (some with embryos). 

 In all, the right ovary was "insignificant" but the left was large and in many cases had 

 large eggs in it. I also dissected five half 'grown to adult specimens from 13 to 26 in. wide. 

 Even in these, the left uterus was large and seemingly ready to receive eggs, the right 

 reduced and indistinct. In all five the right ovary was small and non-functional. The 

 left was always larger (in the 26-in. ray ten times larger) and filled with growing eggs. 



Here is described a progressive gradation from partial to complete unilateraHty in the 

 functioning of the reproductive organs of elasmobranchs. In the butterfly ray, Pteroplatea 

 maclura, both ovaries and both uteri are functional, but in all dissections the left organs 

 were invariably better developed — i.e., the right ones are beginnmg to degenerate. The 

 sharks described (Chlamydoselachus excepted) all have bilaterally functioning oviducts, 

 but unilateraHty in the ovaries in that the right ones only are functional. Finally in the 

 stingrays, Dasyatis say and hastata, complete unilateraHty is found — left ovaries and left 

 oviducts only are functional. Here then are those specializations in the functioning of the 

 reproductive organs which are adumbrated in Chlamydoselachus, the lowest ranking 

 shark and lowest elasmobranch. In the rays as in the frilled shark, there is found the 

 same correlation of unilateral genital organs with a restricted body cavity. In Chlamydo- 

 selachus, the body cavity is narrow but is somewhat long to contain the closely-packed 

 embryos; in the rays the cavity is both short and narrow and in the single uterus the 

 few embryos are rolled up scroll-fashion. 



From other notes made from my dissections and from a rather extensive but widely 

 scattered literature, other similar unilateral functionings of ovaries and oviducts in other 

 elasmobranchs might be given if it seemed necessary to go into the matter further. 



THE ENCAPSULED EGG OF CHLAMTDOSELACHUS 



The encapsuled egg of Chlamydoselachus, as it emerges from the shell gland and 

 passes into the uterus, consists of a large yolk mass with a protoplasmic germinal area. 



