64 DR. LEIDY ON THE HISTORY AND ANATOMY OF 



The genital prolongation has the two caudal set* projecting from it, which are 

 capable of being entirely retracted within the abdomen, from the great extent of the 

 articulating membrane, between the genital prolongation and last abdominal segment. 

 Immediately posterior to the caudal setse are two hook-shaped appendages, which are 

 probably used in retaining hold of the female in coitu. 



The genital and anal prolongations are articulated with each other at their base, as 

 well as with the sixth or last abdominal segment, so that when the one is retracted 

 tlie other must follow. They correspond to the dorsal and ventral plates of a seventh 

 abdominal segment. 



Female. The ovaries are large, and are situated one on each side of the body, 

 extending from within the thorax, at the side of the oesophagus, to the posterior part 

 of the abdomen. Each one is composed of five tubes attached together, and with 

 those of the other side at their filamentary apices. The tubes are of the same length, 

 and within the thorax are straight and narrow, and contain numerous ova in a very 

 undeveloped state, but within the abdomen they become wider, thinner, and much 

 convoluted together, and contain numerous nearly fully developed ova, which together 

 form a large oval mass, occupying with the other the greater part of the cavity of the 

 abdomen. 



The ova are oval in form, somewhat compressed and curved, and are of a yellow 

 colour, with brown streaks upon the larger extremity, a whitish mark upon the 

 small end, and a round spot upon the convexity of its curve. They are placed 

 within the egg-tubes, with their long axis parallel with the course of the latter, and 

 overlie each other at their extremities. 



The five tubes of the ovary form by their junction a short oviduct, which joining 

 with its fellow of the opposite side forms a short vagina, proceeding to the genital 

 orifice between the genital and anal prolongation. 



The hooks developed upon the genital prolongation of the male, exist in a 

 rudimentary form in the female. 



In Perthostoma the oviducts are comparatively twice the lengtli of those of 

 Belostoma, and the ova are oval, without the especial marks existing upon those of 

 the latter. 



Odoriferous Glands. — These consist of two moderately long coecal tubes, situated 

 within the metathorax, beneath the other viscera, and extending into the anterior part 

 of the abdomen. They are convoluted together in such a manner, that after one or 

 two turns the closed extremity is brought close to the termination, both of which 

 extremities are concealed by the passage over them of the ventral cord. They open 

 externally between the coxse of the posterior legs. The character of the secretion I 

 failed to detect. 



