14 Transactions of the Society. 



with processes similar to those described as arising from the interior 

 of the vestibule. In fig. 18 the genital plate and vestibule are 

 shown. They have been artificially turned rather away from each 

 other on their left sides, the vestibule being somewhat twisted on the 

 vagina. The drawing is intended to give an idea of how they would 

 fit against one another if the vestibule were allowed to return to its 

 natural position facing the genital plate. 



The Respiratory System. Fig. 19. 



So far as is known, in all Gamasidse the breathing-organs are 

 trachese ; those from each side communicate with the exterior by a 

 single stigma, which is usually placed between the second and third 

 pairs of legs. This stigma does not open directly to the exterior, but 

 into a long tubular peritreme in the thickness of the chitinous 

 cuticle. This peritreme varies in form according to the species, and 

 is often much undulated or tortuous ; it most frequently opens to the 

 exterior in front of the second pair of legs. 



In the typical species of the genus Uropoda, and indeed in all 

 species if Kramer's definition of the genus be adopted, the ventral 

 plate has large shallow depressions in it within which the respective 

 legs, when folded up, can be laid so as not to project below the body. 

 These depressions are wide, and there is one for each leg of the 

 second, third, and fourth pairs ; they occupy almost the whole of the 

 ventral surface of the body between the coxae of the legs and the 

 lateral margin. Being wide, the depressions come close together, and 

 are only divided from each other by a ridge formed by the narrow 

 strip of the ventral plate which is not depressed. These depressions 

 — if that word can be allowed — are bendings-in of the ventral plate ; so 

 that although each depression is concave when seen from without, yet 

 it is convex when the ventral plate is seen from the dorsal side, i. e. 

 from within the body (of course in order to see it thus it must be 

 dissected off, or else the dorsal plate and all the principal interior 

 organs must be removed). When seen thus, what from the exterior 

 appear ridges between the depressions assume the form of narrow 

 trenches between convexities. 



The stigma on each side of Uropoda Krameri is situated in a small 

 plate-like thickening near the middle of the interior of the depression 

 for the third leg. The peritreme (fig. 19) runs diagonally forward 

 and outward until it reaches the trench (the ridge externally) which 

 divides the depressions for the third and second legs j the peritreme 

 runs along the side waU of this trench and turns round the end of it 

 in a hook-like manner, terminating by a very fine ending in the 

 depression for the second leg. 



From the stigma a short, single tracheal trunk curves backward 

 and upward (into the body) ; from the hinder end of the trunk the 

 whole of the trachese which supply the body proceed. The tracheae 

 are long and excessively fine ; they are entirely unhranched, being 

 only simple tubes of extreme tenuity. This unbranched condition of 



