The Anatomy of Opistlwpatus cincUpes. 73 



A brief but good description is given by Gaffron (1883, p. 51), 

 according to whom the coxal organ forms a furrow with tumid Kps, 

 which may be closed or widely gaping. The epithelium lining the 

 furrow is smooth (not tuberculate) and possesses a smooth cuticula 

 but no '' subepidermoidal layer." 



Good figures have been given by Sedgwick (1888&, fig. 12) and 

 quite recently by Wheeler (1898, figs. 5 and 7), which may be 

 compared with my fig. 18. 



In his recent paper dealing with 11 species and 2 varieties 

 of Peripatus, Bouvier (1900a) states that he found these organs 

 always present, although sometimes rudimentary in the most 

 anterior and posterior pairs of legs. They assume various shapes, 

 some being quite invaginated with the lips almost closed, others half 

 evaginated in the form of a trough, like that in Sedgwick's figure, 

 and others again quite evaginated and forming a voluminous vesicular 

 appendage. The wall of the organ he describes as thin, and, in the 

 case of one species (P. trinidadensis, p. 437), he further mentions that 

 it is without the scale-like secondary papillae, which cover the other 

 parts of the body. Bouvier does not, however, state whether he 

 examined the other species with regard to this last point. 



Sclater (1887, p. 132) had previously already observed the protruded 

 vesicular appendage in P. imthurmi, Sclat. 



I have myself examined some sections of a West Indian species, 

 P. dominica, Pollard (unfortunately not very well preserved for 

 histological purposes), which showed that the basal organs very 

 closely resemble those of Opisthopatus. Indeed I was unable to 

 detect any differences worthy of note, excepting that the retractor 

 muscles seemed more strongly developed. The scale-like secondary 

 papillae were entirely absent and the cuticula appeared to be quite 

 without sculpturing, although somewhat detached and crumpled. 



Coxal organs occur in two other extra-American forms, namely 

 P. tJiolloni, Bouv., from Gabon, West Africa, and P. sumatranus, 

 Sedgw., the locality of which is doubtfully given as Sumatra. 

 Through the kindness of Professor Bouvier I have been able to 

 personally examine a specimen of the former species, while in the 

 case of the latter I conclude from Horst's figures and description 

 (1886) that the structures called by him the " segmental grooves " 

 can be nothing else but coxal organs. From what we know of both 

 these species they must, for the present at any rate, be considered as 

 belonging to the restricted genus Peripatus, with which they closely 

 agree in all the essential characters that have so far been examined. 

 Otlier genera. — In the remaining genera no distinct coxal organ 



