92 J. E. DUERDEN. 



the dorsal directives and the dorsal pair of second cycle mesen- 

 teries. Such an early stage is to be expected on the dorso-ven- 



FIG. Srf. 



FIG. 8 (a-d). Series of diagrammatic figures illustrating the order of develop- 

 ment of the jtwelve pairs of third cycle mesenteries. 



tral succession already established in the case of the second cycle 

 mesenteries (p. 70). 



in 



FIG. S6. 



The succeeding exoccelic chamber on each side lies between 

 the dorsal pair of second cycle mesenteries and the dorso-lateral 



