756 



Bashford Dean Memorial Volume 



In his manuscript Dean states that, at the time of hatching, the yolk sac has been 

 completely resorbed. A small scar (about 8x5 mm.) shows where it last appeared. In 

 a footnote to this manuscript Dean quotes Goodrich's statement (1909, p. 132) that the 

 yolk sac protrudes from the ventral surface of the embryo often after birth [hatching?]. 

 Dean gravely doubts that this occurs in sharks under normal conditions. "I have witnes' 

 sed birth [hatching] in the cases of Cestracion (Heterodontus), Spinax, Raja, Pristiurus, 



Text-figure 65. 

 A young female specimen, 280 mm. (11 inches) long, of Heterodontus japonicus in the collection of the Ameri- 

 can Museum of Natural History. Probably it was obtained at Misaki by Bashford Dean. The color pattern 

 has faded considerably, and is not well shown in the photograph. The mouth cavity has been opened by 

 a lateral incision, here shown closed by several stitches. 

 Photograph, American Museum of Natural History. 



and in no instance was there still an external yolk sac. Viviparous sharks will, however, 

 under the stress of capture frequently give birth to young more or less immature". Very 

 likely, in oviparous sharks, hatching may be sHghtly hastened by handling the egg cap' 

 sules. In his original notes on Heterodontus japonicus. Dean writes concerning the fish 

 observed in the act of hatching: "Yolk sac, so large [si2;e indicated by a circle 3 mm. in 

 diameter], yellow, apparent between pectorals". But Dean does not definitely state that 

 this diminutive yolk sac protruded from the body of the fish. Perhaps it had been drawn 

 into the body, and the yellow color was subsequently visible through the skin. 



Dean's figure of a young H. japonicus aged two weeks after hatching (Figure 84, 

 plate VII) should be compared with Brevoort's figure representing another specimen in 

 approximately the same stage (Text-figure 22, page 690). Dean's specimen was 205 mm. 

 (8.2 inches) long, while Brevoort's measured 216 mm. (8.5 inches). Dean's fish was a fc' 

 male, Brevoort's a male. In the drawing Brevoort's specimen appears to be more slender, 

 and the fins longer. The transverse furrows of the ventrolateral body wall are not so 

 numerous and well-defined in Brevoort's figure as they are in Dean's. The color pattern 

 in Brevoort's figure approaches more nearly that of the adult as portrayed in my Text- 



