718 Bashford Dean Memorial Volume 



Barnhart (1932) notes that it takes eight to ten weeks for the young of H. francisci 

 to hatch from the egg case, at which time the yolk is completely absorbed and the young 

 shark is 14.5 inches long. Eggs have been hatched in the aquarium of the Scripps Insti- 

 tution at La Jolla, California, in June, September and December. Nothing is said about 

 the temperature of the aquarium water in comparison with that of the ocean water at the 

 depths where eggs are found. 



In his brief manuscript containing a summary of his observations on the embryology 

 of Heterodontus japonicus. Dean states that the term of development (before hatching) is 

 reckoned at about one year, with the possibility that it may extend over a period of two 

 years, at an average water temperature of about 65° F. He writes that, in his estimate of 

 the rate of development, he was aided by the fact that eggs found in any one season are 

 usually in about the same stage. This latter statement may need further qualification. 

 Some generalities bearing on this subject are recorded under ''Breeding Season" on page 

 712 of the present article. It is there stated that in the vicinity of Misaki spawning 

 occurs throughout the year, though the special spawning season is evidently the month of 

 March. From the original data contained in Dean's notebook, it appears more likely that 

 spawning reaches its height during the month of April and continues at a rapidly reduced 

 rate during the months of May and June, after which it is almost negligible. As might be 

 expected, there is an increasing range of variation in the stages collected during each 

 month after the first month of spring. Hatching has been observed in April, at which 

 time the young shark is presumably at least a year old. 



In Dean's manuscript there is an outHne for a time scale in which it was intended to 

 give the stage of development that predominates in each month, by reference to Balfour's 

 stages in Pristiurus and other sharks. Unfortunately, the spaces left for the letters indi' 

 eating the stages have not been filled in. There is also a series of diagrams or outline 

 drawings representing developmental stages from the time of spawning to the time of 

 hatching. All excepting the last two (which are outlines copied from Figures 82 and 84, 

 plate VII) are reproduced as my Text-figures 43 to 45. Two of the original drawings are 

 annotated with the names of months. Fortunately these are drawings representing 

 stages for which data would otherwise be lacking. In the legends for Text-figures 43 to 

 45, I have specified the month or months in which each stage seems to predominate 

 according to the information at hand, but we can be fairly certain only for the months 

 of April, May and June. 



Dean records that a total of approximately 200 embryos of Heterodontus japonicus 

 were collected for him at Misaki. In his notebook there is a table giving individual 

 records for 135 living embryos collected during April, May, June and July (up to July 

 6 only). This table is dated at the top, in Dean's handwriting, "Dec. 15, 1904". It is 

 probable that it does not contain any entries subsequent to this date, for all the entries 

 are in chronological order and there are no gaps in the series affording space for further 

 entries. We know that Dean was in Japan (though not continuously at Misaki) from 

 July to October in the year 1900; March to July in 1901; and June to October in 1905. 



