The Emhryology of Chlamydoselachus 557 



The third matter is also based on the great disparity between the slight diminution of 

 the yolk sac and the considerable growth of the embryo. It comes to me in this form — 

 Does the embryo of this viviparous or ovoviviparous shark receive any nutriment from 

 the uterine wall of the mother? The shallow water Httoral tropical nurse shark, Gingly- 

 mostoma cirratum, is also ovoviviparous. It carries in its uteri huge (c. 145 mm. long) 

 blunt'cnded, thick -shelled eggs (Text-figure 16) entirely comparable to those of Chlamydo^ 

 selachus. I have had the good fortune to make extensive studies on Ginglymostoma, the 

 nurse shark, and from these I hope further on to throw light on this question. 



All these data (save those from Deinega's article) were known to Smith when his mo- 

 nograph on the anatomy of Chlamydoselachus was pubhshed in 1937- But in the matter of 

 the reputed unilaterality of the functioning of the oviducal apparatus of Chlamydoselachus, 

 he showed sound judgment in his concluding remarks on the reproductive organs of 

 the female of this shark. Here is his matured statement published before I had made 

 my minute study of Dean's notes presently to be referred to. Smith (1937, p. 449) 

 wrote as follows: 



There is not a single known instance of complete development of the reproductive organs 

 on the left side. Yet it must be borne in mind that the number of specimens that have been de- 

 scribed is still very small. The organs on the left side are developed to such a degree that 

 they can scarcely be called rudimentary. In view of the great variability found in many 

 other organs of Chlamydoselachus, one should not be surprised if the exammation of ad- 

 ditional material should reveal cases in which the genital organs of the left side, or of both 

 sides, are functional. 



In the light of the data given above as to the functioning of the right oviduct only in 

 Chlamydoselachus, there are now to be presented certain data showing that the left ovi- 

 duct also is sometimes functional in this shark. In these data will be found the verifi- 

 cation of Smith's prognosis. 



The Left Uterus Sometimes Functional 



It has already been seen that in the adult, while the right ovary is the predominant 

 one, the left ovary does sometimes contain large eggs; i.e., is functional. Evidence that 

 the left uterus is occasionally functional will now be presented. This is a matter of ex- 

 ceptional interest. 



The earliest intimation, that the left oviduct may contain eggs, comes from CoUett 

 (1897)- In his short and not always clear description of the oviducts of a 1910-mm. 

 specimen, he says that "each expands to a uterus-like sack, of which the right is somewhat 

 larger than the left; both contained immature eggs". There is no doubt that he was 

 referring to the oviducts, but what he meant by "immature eggs" is very obscure. I can 

 only conjecture them to have been wind eggs like that figured by Dean (Figure 51, plate 

 V). In many years' dissections of viviparous sharks and rays, I do not recall ever having 

 found in a uterus an "immature" egg, meaning an undeveloped or unripe or shell-less egg, 

 but I have in the nurse shark found what my notes record as "infertile eggs". I do not 

 recall that I opened one to get at its contents. I did not then know of the term "wind 



