The Embryology of Chlamydoselachus 579 



process — as figured by Nishikawa (my Text'figure 4); and by Dean, Figures 7 and 9, 

 plate I. Or this is very blunt and looks cut off as shown by Garman inText'figure 19. Or, 

 at this end of the capsule, the process is almost or entirely lacking as seen in Figures 2 

 and 3, plate I, and as found in eggs deposited by Dean in the zoological museum of Colum' 

 bia University. Thus one end of the capsule looks "finished" and the other — especially 

 when the process breaks up into tendrils — looks decidedly unfinished. However, the 

 practical disappearance of the process at one end of the capsule, taken in connection with 

 the fact of uterine gestation of the egg, is surely indicative of an evolutionary movement to 

 get rid of the capsule around the egg of Chlamydoselachus. 



Nothing is known as to the method of formation of the capsule and its processes in 

 Chlamydoselachus. This could only be had by dissection of females immediately after 

 capture in the hope of finding capsules still in the glands. How improbable is such an 

 opportunity, the reader will readily realize from considering the habitat of the fish and the 

 difficulty of its capture. However, I have fortunately been able to make such dissections 

 and observations on the nurse shark, Ginglymostoma cirratum, which, as noted, carries 

 in each uterus eggs with large thick'walled blunt-ended capsules. In this capsule, one 

 end is likely to be smaller and seemingly pinched together, more "finished", like that of 

 Chlamydoselachus, while the other is larger, somewhat drawn out and blunter, unfinished 

 looking — this end being presumably that last formed. In Text'figure 16 one cannot make 

 this distinction very readily, because the ends are very much alike. But since I have 

 examined scores of these eggs, I am satisfied that the longer and broader end of the capsule 

 is the younger. Furthermore, the blunter end is plainly the younger in the eggs shown in 

 Text-figure 21. Then there is another criterion on which to base judgment. The egg 

 (yolk mass) is placed excentrically in the shell (Text-figures 16 and 21). This results from 

 the fact that the jelly-like substance lining the shell forms a larger plug in one end of the 

 capsule. In these unequal-ended capsules of the nurse shark, this larger amount of jelly 

 is in the "unfinished" or younger end as may be seen in the figures referred to. 



Now it is clear that Ginglymostoma is the last of a line of oviparous sharks, and that 

 like Chlamydoselachus, it is an ovoviviparous selachian well on the way toward a vivipa- 

 rous mode of reproduction. As such, Giyiglymostoma like Chlamydoselachus might be 

 expected occasionally to retain tendrils at the larger, blunter, younger, or "unfinished" 

 end of its capsule. That it does this is shown in Text-figure 21. Furthermore, while at 

 Tortugas in 1912, I fortunately by dissection learned how and when these tendrils are 

 formed. The facts as ascertained will now be given from my notes. 



FORMATION OF TENDRILIFORM PROCESSES 



On June 16, 1913, I dissected several female specimens of Ginglymostoma and found 

 that "No. I fish had in the section of the left oviduct just behind the shell gland an egg 

 whose backward [really its anterior] end was covered with a hard tough shell (like any of 

 the eggs in the uterus) with the short blunted base of the absent horns drawn toward each 

 other, as may be seen in Carman's drawing (1913, Fig. 5, pi. 59). The posterior end of the 



