The Embryology of Chlamydoselachus 581 



drawings (Figures 7 and 9, plate I). More markedly does this contrast appear in Gar^ 

 man's drawing (Text'figure 19 herein) and in Dean's two oblong eggs (Figures 2 and 

 3, plate I). 



Not being able to decide by observation which is the anterior or older end of the 

 egg capsule in Chlamydoselachus, let us turn for comparison and explanation to the very 

 similar egg shell of the nurse shark, Ginglymostoma, in which I have settled the matter 

 by dissection and direct study. My observations on the formation of the process of the 

 egg shell of Ginglymostoma make clear when and how the long processes seen on the cap' 

 sule of Chlamydoselachus are formed. Here let the reader note the twisted processes in 

 the figures just referred to, and the tendriliform holdfast organs seen on Carman's egg 

 and on Dean's oblong specimens. The bluntly conical, the "finished" end, is the anterior, 

 the older, the first formed; the twisted and the tendrilform ends are the younger, posterior, 

 or later formed. So also one can understand the formation of the very much frayed-out 

 tendril'bearing tips shown in Figures 13 and 14, plate I. The finished ends of the capsules 

 plainly came through the shell gland first and quickly, while the tendriliform ends came 

 last of all, lingered and were then formed. 



It is difficult to explain the formation of the three round egg cases and their short 

 blunt processes at each end as portrayed in Plate I. However, the smaller process of the 

 egg in Figure 6 was probably formed last. It seems likely that, in some way not clearly 

 understood, each end of a round capsule, as it passed through the sphincter at the hinder 

 part of the shell gland, remained in the orifice the same length of time and received the 

 same treatment. And as a result the two processes of each capsule are practically identi' 

 cal. It would seem that had these eggs at the close of shell formation lingered in passing 

 through the sphincter the posterior process would have become long'drawn-out as seen 

 in the oblong capsules and as observed by me in process of formation in the nurse shark. 



Thus the structure of the posterior or last'formed end of the egg capsule of Gingly^ 

 mostoma with its abortive tendril'like processes, affords a clue to and explanation of the 

 formation not only of the curved finger-like process on the normal egg capsules of Chlamy- 

 doselachus but also of the aberrant tendriliform ones of the atypical egg shells. 



EXTERNAL EMBRYONIC DEVELOPMENT 

 OF CHLAMTDOSELACHL/S 



In earlier parts of this paper I have discussed the breeding habits and have described 

 the reproductive organs of the frilled shark. These sections are based on Dean's scattered 

 but invaluable notes and upon the scanty literature. These studies have considerably 

 extended our knowledge of the reproductive activities of this shark and have laid a founda- 

 tion for a study of its external embryonic development. For this there is at hand practical' 

 ly nothing but the excellent drawings reproduced in the plates. In the almost complete 

 absence of notes, all that can be done is to arrange the drawings in the order of develop- 

 ment of the embryos and to describe these as accurately as possible, always comparing 



