56 



ON CLASSIFICATION. 



posed essentially as in this and the two preceding classes. But 

 the total number of somites of the body never exceeds twenty. 



Fig. 28. 



Fiff. 29. 



Fig. 29. — Longitudinal and vertical 

 section of the abdomen of a 

 male Cockroach (Blattci). — 1, 

 2, 3, 4, &c., terga and sterna of 

 the abdomen ; t, testis ; v, 

 aperture of the vas deferens ; 

 A, anus. 



