60 ARTHUR DENDY. 



present as in the adult. In the front of the mandible the two 

 large cutting teeth of the adult are represented each by three 

 distinct conical, pointed teeth, a larger one behind and two 

 smaller ones in front. These three teeth probably fuse to- 

 gether in later life. Similarly in the premaxillse each of the 

 two large cutting teeth of the adult is represented by three 

 distinct conical, pointed teeth, of which the outermost is much 

 larger than the other two. These also probably fuse together 

 in later life.^ I could find no vomerine teeth in the specimen 

 specially investigated as to this particular. 



The parietal eye is no longer visible externally, but its 

 position seems to be indicated by a small median tubercular 

 scale lying a short way in front of the first nuchal spine. 



The colour of the dead animal is dirty white, irregularly 

 mottled, and banded with grey. The longitudinal striping 

 has disappeared except under the throat and chin, where it 

 still remains distinct, but with the wliite stripes ^ now narrower 

 than the grey. The transverse banding is still clearly recognis- 

 able on the back and tail. The whitish or yellowish spots, so 

 conspicuous in some adult specimens, have not yet appeared ; 

 they would seem to be formed by gradual encroachment of the 

 grey pigment over the paler parts of the integument. 



4. Summary and Discussion of PRiNcirAL Embryological 

 Observations. 



{a) The Formation of the Germinal Layers. 



The question of the origin of the germinal layers, and 

 especially of the hypoblast, is one of great difficulty, and 1 

 have slightly altered my views on the subject since writing my 

 summary of results (4) some time ago. 



The blastoderm spreads around tlie yolk at an extremely early 



1 As was surmised by the late G. Baur (' Anat. Anz.,' Bd. xi, p. 43G) ; cf. 

 also Giintlier, ' Pbil. Trans.,' 1867, pt. ii, p. 8. 



^ These stripes appear to be represented by longitudinal rows of light- 

 coloured scales on the under surface of the head of the adult animal. 



