582 Bashford Dean Memorial Volume 



each stage with the one just preceding it and noting the progress in development of 

 various organs. Here I must acknowledge my indebtedness to Scammon's excellent work 

 published in 1911. 



EARLY DEVELOPMENT 



Since the total number of gravid females (26) obtained by Dean was not large, it is 

 not surprising that he secured very few fertilized eggs in early stages of development. 

 None of these has been preserved intact, nor do I find among Dean's materials any blasto- 

 derms excised from the eggs and preserved in toto — either mounted or unmounted. My 

 only information concerning this material has been derived from a few scattered notes, 

 a small number of serial sections, and a few drawings — some in a more or less finished 

 condition, others mere sketches. 



BLASTULAE 



Nishikawa (1898) is the only student of the frilled shark who has published any 

 observations on eggs with early blastoderms. He states that "The blastoderm has a yel- 

 lowish red color, as in other sharks. The earliest stage that I have been able to obtain 

 was nearly circular in form and had a diameter of 1.3 mm". This is confirmed by my 

 observations on the eggs of Ginglymostoma. The blastoderms were noted in 1912 as 

 "yellow spots", always placed "asymmetrically on the egg, generally in the corners so to 

 speak". In 1914 my notes read — "Blastoderms very small, even minute [unfortunately 

 they were not measured], placed excentrically; in one lot of eggs from one female, 7 at 

 one end, and one on one side of egg". These blastoderms in Gmglymostoma were so 

 small that I found them only by their color. But when removed and placed under the 

 microscope I could make out the cells. 



This colored spot seems to be a characteristic feature of the eggs of the Elasmo- 

 branchii. Leydig (1852) was, so far as I know, the first to figure and describe the "orange- 

 yellow spot" on an elasmobranch egg. On the egg of Pristiurus melanostomum, he found 

 it at the end of the egg next to the rounded end of the capsule — i.e., that with short horns, 

 the finished or older end of the egg shell of this oviparous fish. It measured c. 3.2 mm. in 

 diameter. Balfour (1885, p. 222) also found this spot on the eggs of Pristiurus, on the ova 

 of two species of Scyllium, and on the eggs of Raja sp. He states that these blastoderms 

 were asymmetrically placed on the eggs of Pristiurus and Scyllium. Haswell (1897, p- 97) 

 found the yellow spot at the broader (older) end of the egg shell of Heterodontus philippi 

 of Australia. Dean shows this spot in his plates of the development of Heterodontus 

 japonicus, which will illustrate Article VIII of this Volume Haswell, in his preliminary 

 report on the development of Heterodoiitus philippi (1897), says "The blastoderm in its 

 earUer stages, appears to the naked eye, as in other Elasmobranchs, as a circular reddish 

 orange spot around which is a narrow light yellow band. When this orange spot has 

 attained a diameter of about 2 mm. it assumes an oval shape". Then Haswell generaHzed 

 about this spot thus — "There can be little doubt . . . that the 'orange spot', which forms 

 such a striking feature of the egg of an Elasmobranch in its early stages, has been handed 



