544 



LOUISE SMITH 



Of the wholly new structures the only examples are the 'little 

 horns' and lingual cartilage. They are no exception to the 

 above rule, but first appear as a collection of chondrioblasts 

 close to the basibranchial — the former, in stage II, and the 

 latter, in stage III (fig. 37) — and later develop hyaline matrix. 



Of the cartilages which disappear entirely, the second and 

 third epibranchials are the type. They follow the method of 

 the larval first epibranchial in degenerating in an anteropos- 



Fig. 3 Millimeter-paper reconstruction of metamorphosing first epibranch- 

 ial; lateral aspect. Stars indicate location of mitoses. The degree of degenera- 

 tion of the remaining portion of the old epibranchial is shown by the amount 

 of stippling. X 50. 



terior wave. First they lose their connection anteriorly with the 

 rest of the visceral skeleton (fig. 28), and then the disintegration 

 advances more and more posteriorly until they are wholly lost. 

 In the breaking down of the branchial plate it is interesting 

 to note that the first change comes in a deepening of the groove 

 at which it articulates with the basibranchial, giving the articu- 

 lation almost an adult appearance as seen in cross-section (figs. 

 30 and 24), but that the actual degeneration begins in the middle 



