375 



A reference to Figs. 3 and 4 shows the mode of development of the 

 claw. In Fig. 3 we see the rudiment of the claw investing the end of the 

 digit. It consists of a cap of keratinoid material staining yellow with 



Malpighian 

 Layer 



Eponychium 



Krallenplatte 



Krallen- 

 Neonychiiim sohle 



Fig. 3. Median longitudinal section through the end of the third digit of the 

 right manus of a 9 cm foetus of T. conurus. 



picric acid. In this rudiment three portions can be made out. The 

 dorsal portion, in which a very distinct fibrous structure is already 

 apparent, is the future Krallenplatte. The fibrous layer investing the 



Eponychium 



Krallenplatte 



Neonychium 



Krallensohle 



Fig. 4. Similar section, from a 12.5 cm foetus. The thickness of the eponychium 

 is much exaggerated in both figures. 



ventral surface of the Malpighian layer is the Krallensohle. In the 

 superficial part of the ventral and terminal region of the claw rudi- 

 ment the fibrous structure is much less pronounced. This portion, 



