500 KtCHARD EVANS. 



of the fourth pad. Fig- 24 represents the renal organ of the 

 second pair of legs. The only parts represented, here are 

 the ccelomic end-sac, and an undifferentiated short duct 

 which passes from it to the exterior. Figs. 27 and 28 show 

 a similar reduction of the renal organs of the two pairs of 

 legs situated in front of the genital orifice. In both cases 

 they consist of a small ccelomic end-sac and a short narrow 

 duct which passes to the exterior. The examples given 

 above suffice to show that there is a considerable amount of 

 difference in the structure of the renal organs in the various 

 parts of the body. The most prominent feature is the sim- 

 plification of structure towards either end of the animal. 



The coelomic end-sac presents in section an irregular and 

 collapsed appearance, but is easily demonstrated in the adult. 

 In the middle part of the body it extends through several 

 sections, but is much smaller towards either end of the 

 auiuial. Its walls are thin and seem to consist of two layers 

 of cells, which are flattened out though not to any great 

 extent (figs. 29 and 30). 



The funnel has a rim which projects into the cavity of the 

 coslomic end-sac, and is never provided with cilia. Its walls 

 consist of an internal lining of closely packed columnar cells 

 with deeply staining nuclei, and an external layer of flattened 

 cells (figs. 29 and 30). 



The coiled tube and the bladder have- practically the same 

 structure as the coelomic end-sac ; the lining cells of the 

 former, however, are less flattened than those of the end-sac, 

 while those of the bladder are more so, and strongly contrast 

 with those lining the short duct which passes from the 

 bladder to the exterior (fig. 31). 



(e) The Female Reproductive Organs: — When an 

 adult female is opened the first structures visible are either 

 the stomach or the coils of the uteri, and the ramifications of 

 the slime-glands, which extend backwards as far as the ovary. 

 In some cases the coils of the uteri are above the stomach 

 and completely conceal it, but in others they are below it and 

 are hidden bv it. In either case the branches of the slime- 



