The Embryology of Heterodontus japonicus 



707 



six inches in length. The spirals are very broad and, in part, hide the body when viewed 

 laterally; at the base they narrow quickly and terminate bluntly, and are not produced into 

 tendrils. Beach-worn examples generally have the terminations more or less frayed. 



Cestracion [Heterodontus] gakatus [Text-figure 37c] ■• Of smaller size; about four inches 

 and a half in length. The spirals are not very broad, and in no part hide the body completely; 

 basally they become narrow and are produced into long flattened tendrils. In the most 

 perfect specimen examined, each tendril is 90 inches in length, and tapers to the slenderest 

 thread, becoming tangled and knotted like a skein of silk. They are, however, very tough, 

 and may be unravelled without fear of breaking. One of the tendrils terminates in a thick- 

 ened tag (shown in the figure) which, although doubtless an individual pecuHarity, indicates 

 that the tendrils are entire. 



Further, Waite calls attention to the fact that the appendages, with which the egg 

 capsules of sharks are furnished, serve to moor them in some suitable situation, otherwise 

 they would be likely to be knocked about to the detriment of the contained embryo, or 

 might even be washed ashore where their destruction would be certain. The spiral 

 appendages of Heterodontus philUpi are no exception to the rule; the elastic flanges permit 

 the egg to be forced further into a fissure, whence extraction is resisted by the free edges 

 of the ribbon catching against the rocks. Although, in a lesser degree, the egg case of 

 H. galeatus possesses these spirals, they do not appear to have the same use; for attach- 

 ment is here effected by the entanglement of the tendrils among seaweed. 



The egg capsule of H. francisci is figured by Daniel (1934, also in earlier editions). 

 His figure is reproduced here as my Text-figure 38. This 

 capsule lacks tendrils and bears a general resemblance 

 to the egg capsule of H. phillipi; but it is more slender. 



Text-figure 38. 

 Egg capsule of Heterodontus 



francisci. 

 After Daniel, 1922, Fig. 254, p. 318. 



Text-figure 39. 

 An egg case of Heterodontus 

 japonicus with an opening 

 cut to show the young em- 

 bryo within. The cleft in 

 the upper left-hand portion 

 of the figure follows the line 

 of the respiratory groove. 

 After Doflein, 1906, p. 209. 



