DEVELOPMENT IN ECHIDNA 



17 



that in the region of the navel at the sides of 

 the body a pair of epidermal thickenings was 

 present (Fig. 6a, ma). Each of these extended 

 over a space of perhaps forty sections, and 



Fig. 6b. — ^Echidna: Semon's Embryo. Series of 

 Transverse Sections through the Primary- 

 Primordia shown in Figs. 5 and 6a. 



represented altogether a strip three times as 

 long as broad (Fig. 6b). The cutis also under- 

 lying these thickenings was specially differen- 

 tiated, owing to an accumulation of nuclei and 



2 



