752 



Bashford Dean Memorial Volume 



around the base of the yolk stalk in Figure 74 probably represents the optical effect of an 

 oil globule in the yolk mass. 



The only remaining figure showing the vitelline vessels of Heterodontus japonicus is 

 Figure 81, plate VII. This represents a much later stage. The large vessel on the right 

 side of the figure is the vitelline artery; therefore the embryo must have reversed its 

 original orientation on the yolk sac. A profuse system of vitelline veins is distributed to 

 the left side of the figure (original right side of the yolk sac). Evidently there is a similar 

 group on the opposite side, as in Figure 78, plate VII. 



Text-figure 59. 

 An embryo of Heterodontus japonicus shortly before hatching, showing its coiled condition and its 



orientation within the capsule. 



r. a., respiratory aperture. 

 From a drawing left by Bashford Dean, but evidently not his handiwork. It has been necessary to correct the positions 



of the gill-clefts, eye, mouth, and nasal aperture. 



HATCHING AND THE NEWLY HATCHED YOUNG 



The part played by the egg capsule in the mechanics of hatching is described, for 

 Heterodontus japonicus, on page 709. It has already been mentioned that, in his notebook. 

 Dean records the length of a nev^^ly hatched Japanese Bullhead Shark as about 7 inches 

 (180 mm.). This was the length of the fish observed in the act of escaping from the egg 

 capsule. A newly hatched fish, in dorsal view, is portrayed in Figure 83, plate VII. 



