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Bashford Dean Memorial Volume 



Text-figure 44. 

 Outlines representing stages in the early development of Heterodontus japonicus. The stages shown in A and 

 B are most abundant in collections made in June; the stage shown in C is probably representative of the 

 month of July. In A, the extent of the area vasculosa is indicated by dotted lines; in B and C, the principal 



blood vessels are represented by solid lines. 



From drawings left by Bashford Dean. 



variation was greater: there were embryos of all stages from late cleavage to one of 31 mm. 

 total length. The average condition was somewhere between the stages shown in Text- 

 figures 44a and 44b. It should be noted that by this time the average condition no longer 

 represents accurately the rate of development of eggs spawned in April, on account of the 

 lag occasioned by continued spawning. Of the 42 eggs taken in July, the majority were 

 collected on July 3 and opened the same day; the others were taken on July 4 and opened 

 on July 6. Here, there are surprising numbers of gastrulae and of slightly later stages, 

 which can hardly be considered as representative of this month; but there are twelve 

 embryos ranging from 15 to 35 mm. long. For July as a whole we have no adequate data 

 indicating the average stage of development, but in view of what follows we assign 

 Text'figure 44c to this month. The original drawing reproduced as Text-figure 45a bears 

 the annotation "Aug-Sept". The next later stage, represented by Text-figure 45b, we 

 assign to October because the following one, portrayed in Figure 82, plate VII, is marked, 

 on the original, "Nov-Dec". 



The newly hatched young, in dorsal view, is represented by Figure 83, plate VII. 

 A slightly older specimen, in lateral view, is portrayed in Figure 84, plate VII. In his 

 manuscript Dean states: "In capsules that have long been incubated, I have found in 

 April the only stages where the young is about to escape from the capsule". He records 

 also that "in a single instance the act of hatching was observed". This event took place 

 early in April, and is described on pages 709 and 753 of the present article. It is important 

 to note that this specimen had been collected only a few days previously. The young 

 shark at hatching is said by Dean to measure about 7 inches (180 mm.) long. As indicated 

 by the original notes, this measurement refers to the single specimen of H. japonicus 

 observed in the act of hatching. 



