1883.] 223 [Jeffries. 



By the eighteenth day, or rather during the nineteenth day, 

 many changes have occurred. The epitrichial layer (figs. 17a 

 and 23) has assumed its final form ; the cells have become irregu- 

 larly polygonal ; regular hexagonal celled patches are rare ; the 

 nuclei are decidedly indistinct and the contents granular. In 

 fact the cells resemble, except in their regular hexagonal outline, 

 Kerbert's figure of the granular layer at this age. That this is 

 the epitrichial and not the granular layer I believe for the follow- 

 ing reasons : — 



Kerbert does not describe the epitrichial layer but says it 

 becomes lost. 



I have specimens showing this layer outside the granular layer. 



I have specimens showing this layer in the depth of folds 

 where the two surfaces are touching and nothing could have been 

 shed. 



That this is the true state of affairs I feel more certain on 

 account of some section of the toe and claw which were doubly 

 stained with eosin and French blue. Such a mixture turns all 

 acid substances deep blue, while all alkaline and protoplasmic 

 bodies take on the eosin red color. Now, fortunately, I have on 

 two or three occasions in staining sections, colored this coat deep 

 blue and all the rest red. Such specimens of course are more 

 easily studied than those worked out by caustic potash solutions 

 alone. 



Below the epitrichial layer (fig. 17) the granular layer remains 

 much the same and both show a tendency to split off from the 

 horn-cells below. The horn-cells have become more numerous 

 and the oldest denser. The rete mucosum cells seem to be 

 smaller and more irregular. The pigment cells spoken of before 

 have entirely disappeared. 



From this time on no important changes occur in the epiderm. 

 The horn-cells continue to be formed from the mucous layer and 

 mature. At hatching the epitrichial and granular layers are shed 

 thus leaving the scutae in their final condition. 



CLAWS. 



Claws exist on the ends of the toes and often on the end of 

 the first finger ; on the end of the second finger they are rare. 1 



r iFor a detailed list of the occurrence of claws, see my article in Proc. Bost. Soc. 

 Nat Hist., Vol. xxi (1881) po. 301-306. 



