The Embryology of Heterodontus japonicus 



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Text-figure 63. 



A position sometimes assumed by a newly hatched Heterodontus japonicus when resting on the bottom 



of the aquarium. 



From a drawing left by Bashford Dean. The gill-clefts have been redrawn in a more nearly correct position. 



swam easily and well, it showed varied movements of its pectorals: it bit, retreated and ad- 

 vanced, it stood on the defensive, and it opened its mouth widely [Text-figures 64b and 64c] 

 as though to inspire fear. During [ordinary] breathing [Text-figures 64a] it showed normally 

 only the most anterior teeth. 



The color of the fish at hatching is dark [Figure 83, plate VII] with a series of light 

 bands: it is covered with a dense "bloom" of mucus. Two weeks later [Figure 84, plate 

 VII] it has grown 25 mm.; it has changed color, shows a kind of opisthure', holds its fins 

 more rigidly. The present figure indicates that down the sides of the body, in this as in 

 [some] earlier stages, there is a row of (16-17) deep vertical creases immediately behind the 

 gill-slits. They suggest a continuation of the line of the gills, with which obviously they have 

 nothing to do. One reflects that it would be easy for an enthusiast to construct a phylogeny in 

 which these deep creases fused with gut pouches and became of respiratory value. The 

 spiracle is still of considerable size, and the dermal denticles are prominent. The latter 

 condition is doubtless protective, guarding against injury from rubbing, and correlated 

 with a long period of incubation in a capsule. 



A B \ r^ C 



Text-figure 64. 



Drawings showing the mouth of a newly hatched Heterodontus japonicus in three different poses: 



A, during ordinary breathing; B, moderately and C, widely open. 



From drawings left by Bashford Dean. 



'Opisthure: The posterior end of the caudal axis of certain fishes and embryos of fishes, which degenerates into a rudimentary 

 organ, or becomes absorbed in the permanent caudal fin developed in front of it (Century Dictionary). 



