Coxal glands of the Arachnids. 261 



which shortly passes into the exit tubule. The exit tubule joins 

 with that of the other side, and the two have a common outlet just 

 behind the mouth. There is a diverticulum from the striated divi- 

 sion, running- posteriorly (CR), called the "reservoir" by Bouviek, 

 the position of which can be gathered from the diagram (Fl). 



Bouviek (1905), whose magnificent work is mainly systematic, 

 does not figure the saccule and collecting tubule of the salivary 

 gland, but they have been described and figured by v. Kennel (1886) 

 in embryos of the American species P. edwardsii and P. torquatus. 

 V. Kennel however says that in the adult the saccule disappears 

 and the collecting tubule is closed. 



Sedgwick (1888) also describes the saccule and collecting tubule 

 of the salivary gland in embryos of P. capensis, remarking that they 

 persist in the adult, and this is certainly also the case in the spe- 

 cimens examined by myself, in all of which the saccule is clearly 

 present and the collecting tubule open. In P. nicaraguensis (photo 50) 

 the saccule and collecting tubule are somewhat reduced in size as 

 compared with those of the typical nephridium, but in P. jamai- 

 censis (photos 48, 50 a) they appear quite normal. 



Peripatus also aft'ords an excellent example of the way in which 

 the extension of one organ, may lead to atrophy of others which 

 were originally its equal. In most species of Peripatus the striated 

 diverticulum (reservoir) of the salivary gland extends posteriorly to 

 the third leg, and the nephridia of the first three legs have lost 

 their striation. In P. janiaicensis however the striated part 

 of the salivary gland stretches back as far as the twelfth leg, 

 according to Bouvier, although in my specimens it does not 

 extend beyond the seventh or eighth leg. However this may 

 be the nephridia of legs six to twelve inclusive have all become 

 modified in the same manner as those of the first three legs, that 

 is, they are very small and have lost their striated part and vesicle. 

 But this modification does not affect the large nephridia of the 

 fourth and fifth legs, which in P. jamaicensis are relatively larger 

 and the striation of the cells more distinct than in the other two 

 species examined. It is difficult therefore to be sure whether the 

 salivary reservoir or the large nephridia of legs four and five have 

 had most eft'ect in reducing those which lie more posteriorly, but 

 the fact remains that in P. jamaicensis the excretory functions of 

 the first fourteen segments are performed by three large systems 

 of well defined striated tubules, whereas other species, in wiiich 



