212 



CHELONIA. 



development (fig. 133). The chief peculiarity in the form of the 

 embryo (figs. 131, 132, and 133) is caused by the development 

 of the carapace. The first rudiment of the carapace appears in 

 the form of two longitudinal folds, extending above the line of 

 insertion of the fore- and hind-limbs, which have already made 

 their appearance (fig. 131). These folds are subsequently 

 prolonged so as to mark out the area of the carapace on the 

 dorsal surface. On the surface 'of this area there are formed the 

 horny plates (tortoise shell), and in the mesoblast below the 

 bony elements of the carapace (figs. 132 and 133). 



Au 



E nr 



FIG. 133. CHELONE MIDAS, THIRD STAGE. 

 Letters as in fig. 131. r. rostrum. 



Immediately after hatching the yolk-sack becomes withdrawn 

 into the body ; while the external part of the allantois shrivels 

 up. 



BIBLIOGRAPHY. 

 General. 



(154) C. Kupffer and Benecke. Die erste Entwicklung am Ei d. Reptilien. 

 Konigsberg, 1878. 



(155) C. Kupffer. "Die Entstehung d. Allantois u. d. Gastrula d. Wirbel- 

 thiere." Zoologischer Anzeiger, Vol. n. 1879, PP- 5 2 ' 593' ^ I2- 



Lacertilia. 



(156) F. M. Balfour. " On the early Development of the Lacertilia, together 

 with some observations, etc." Quart. J. of Micr. Science^ Vol. xix. 1879. 



