THE WAI^AYAN SPECIES OF ONYCHOPHOHA. 69 



majority of individuals of the genus Eoperipatus, in wliich 

 the common duct is placed in the median chambei* and does 

 not pass under the nerve-cord. 



The Second Somite from the Posterior End {sonV^). 

 — In both male and female, the modifications which this pair 

 of somites undergo are similar to those passed through by 

 any pair of somites situated further forward, except that the 

 renal duct does not become elongated and coiled^ and that 

 in the adult male it tends to disappear (PI. 8, figs. 20h, 

 ren. or., and 21 h, ren. or.). 



(6) The Development of the Male Accessory Glands. 



The Last Pair of Somites {som"). — In the female 

 the last pair of somites disappears almost immediately after 

 their formation ; but in the male they are destined to 

 become the accessory glands. In an embryo slightly older 

 than the one shown in fig. 4 on PI. 5 they are fully 

 formed and crescent-shaped. In a somewhat older embryo, 

 oblique sections of which are shown in figs. 20 « and 20 6 

 on PI. 8, they are situated close to the posterior ends of 

 the nerve-cords, and curve round it in such a way that they 

 come in contact with the ectoderm of the ventral surface 

 just in front of the anal slit, though they do not yet open to 

 the exterior. In an embryo slightly older than the one shown 

 in fig. 5 on PI. 5 the last pair of somites open into the 

 exterior, and have already assumed a tubular form, though 

 they are still short (PL 8, figs. 21 a and 21 h, m. a.g.). 



The above account proves that the male accessory glands 

 of Eoperipatus are in part mesodermal, and that the cavity 

 of their inner moiety is coelomic. From this conclusion it 

 follows that the male accessory glands are homologous with 

 the renal organs. Therefore in Eoperipatus the salivary 

 glands, the renal organs, the genital ducts, and the male 

 accessory glands are all homologous organs, derived from 

 the mesoblastic somites, and put in communication with the 

 exterior by means of a short invagination of the ectoderm. 



