OUTLINES OP THE DEVELOPMENT OF THE TUATAliA. 57 



mencemeut of this stage. This growth forms a darkly stain- 

 ing mass of tissue, apparently derived from proliferation of the 

 epiblast lining the nostrils, into which it gradually merges.^ 

 The epiblastic lining of the nostrils is still perfectly sharply 

 defined on its outer aspect from the surrounding mesoblast. 



(4) Owing to development of the eyelids the paired eyes 

 have acquired their proper elongated appearance. 



(5) Pigment is present in the parietal eye (figs. 104, 105, 

 Pa. E.), rendering it conspicuous externally as a small black 

 circle surrounding a white spot. In the younger embryos of 

 this stage, where the outlines of the optic lobes and cerebral 

 hemispheres are still visible externally, the parietal eye is now 

 seen to lie above the apparent centre of the diamond-shaped 

 roof of the thalaraencephalon. As far as one can judge, it has 

 become median in position. 



(6) Teeth have appeared in both upper and lower jaws, in- 

 cluding the palatine teeth, but 1 have not succeeded in detecting 

 any vomerine teeth. 



(7) The tail is to a large extent uncoiled, and lies with its 

 apex pointing backwards against the animal's right side, as 

 shown in fig. 104. A distinct corrugation, indicating the 

 future crest, already appears on its dorsal aspect. 



(8) The digits have become greatly elongated, and the limbs 

 have much the same proportions as in the adult. 



(9) Pigment has made its appearance in the general integu- 

 ment, forming a very conspicuous and remarkable pattern, as 

 shown in figs. 104 and 105. On the back and sides of the body 

 and tail this pattern takes the form of narrow, discontinuous, 

 longitudinal stripes of white on a grey ground, combined with 

 a less strongly marked development of much broader, transverse 

 bands of white, especially distinct about the root of the tail. 

 The limbs also are marked with longitudinal streaks and dashes 

 of white. In the mid-dorsal line of the body there is a very 

 characteristic tiarrow moniliform stripe, composed of a row of 

 small white spots which seem to indicate the position of the 

 spines of the future crest. On the dorsal aspect of the head 



^ Cf. Addendum at the end of this paper. 



