1905.] GEPHYREAX WORMS OF ZAXZIBAU, ETC. 33 



hooks of tlie Physcosoma type that lie in the introvert. Generally 

 the hooks in Phascolosoma are simple, slightly curved structures, 

 and in only one other form, the Ph. papilliferum of Keferstein 

 ( = Ph. dissors Sel. & de Man), do the hooks, so far as I know, 

 acquire the features that ai'e generally found in those of a 

 Physcosoma, namely the greatly curved apex borne on a broad base, 

 the more or less sharply differentiated clear central space, and 

 often an accessory lobe. As regards the internal anatomy, the 

 following are the most important feat^^res : — There are four 

 retractors, of which the ventral arise fairly close to the nerve-cord 

 and just behind, the dorsal just in front of, the middle of the 

 body ; these unite very soon to enclose the oesophagus, above which 

 lies the simple contractile vessel. The intestine is not much 

 twisted, and the rectum, which is moderately long, opens a little 

 in front of the origin of the dorsal retractors ; a little in fi'ont of 

 the anal opening again are the openings of the nephridia, w^hich 

 latter are short, rather broad, and unpigmented. The intestine 

 is held to the hind end of the body by a fine muscle-strand, and 

 two other somewhat stouter strands run («) from the left side 

 of the nerve-cord to the commencement of the intestine, and 

 {b) from near the anus, along the rectum, to the intestine, Tw-o 

 very distinct eye-spots may be seen just above the mouth. 



Externally the body is covered with numerous, conical, often 

 brown-coloui'ed papillae ; in the middle, however, these are lower, 

 less numerous, and more finger-shaped. These papillae, moreover, 

 extend a little w-ay up the introvert, gradually becoming fewer and 

 lower, till they reach the rows of hooks (which reach more than 

 halfway back along the introvert) ; in betw^een the row-s they 

 appear as flattened elliptical bodies Avith a conspicuous central 

 opening. 



TV. Genus Cloeosiphox. 



14. Cloeosipho.v aspergillum Quatrefages. 



Selenka, torn. cit. p. 126 (1883). 



Log. Ohwaka Bay, Zanzibar ; 2 specimens. British East 

 Afiica ; 1 specimen. 



Y. Genus Aspieosiphox. 



15. AsPiDOSiPEOX ELEGAXS Cham. &j Eysenh. 



Selenka, torn. cit. p. 124 (1883) ; Sluiter, ISTatuurk. Tijdschr. 

 Ned. Ind. 1. p. 116 (1890), and Siboga-Exp. p. 19 (1902). 



Loc. Wasin, British East Africa. 



Hah. Among coral, at low tide. 



Several specimens. In Selenka's key to the species of this 

 genus he includes A. elegans amongst those in which the anal 

 shield is calcified. But there is certainly no calcification in the 

 specimens I have seen, nor does Selenka mention the fact in his 

 description. 



Proc. Zool. Soc— 1905, Yoi.. I. No. III. 3 



