108 EDWIN 8. OOODRICH. 



coelora." From this description the relations of the proble- 

 matic organs are by no means easy to nnderstancl^ and the 

 author himself seems to be very doubtful as to their existence 

 (11 and 12). Ikeda looks upon the perianal sinus as apurelj'- 

 artificial space. This, indeed, may be the case in some 

 species, as, for instance, in the larva I obtained in Ceylon. 

 In this Actinotrocha (fig. 9) the coelomic epithelium is 

 separated in the perianal region from the outer body-wall 

 only for a short distance above and below the tliick ciliated 

 ring. The chink between the two layers contains no clear 

 space at all, but appears to be filled up with a connective 

 tissue of fine mesoblastic fibres — possibly coagulation pro- 

 ducts in a jelly-like substance. 



Menon (13) has described a perianal sinus, and de Selj's 

 Longchamps appears to have found a similar space in his 

 species (16). Such a cavity certainly seems to exist in the 

 species from Faro (fig. ],^)a. s.) when the perianal band is 

 expanded ; but when it is withdrawn together with the anus 

 (as it frequently is), so that the cilia point inwards into a 

 temporary posterior depression, the coelomic epithelium is 

 stretched tightly over the inner surface of the ciliated ring, 

 and the cavity then vanishes almost completely. The loose- 

 ness of the coelomic epithelium in this region, in fact, appears 

 to be only a device whereby the invagination of the perianal 

 ciliated ring can be brought about. The thin posterior 

 septum, with radiating and probably contractile bauds (fig. 

 1), forms a complete membrane shutting off the perianal 

 sinus. It is not formed of separate " brides mesenteriques," 

 as suggested by de Selys Longchamps (16). 



The problematic posterior trunk nephridia have been 

 severely dealt with by Menon and Ikeda (13 and 9) ; I 

 need only add that my own observations entirely support 

 their view and Masterman's own recent statement that '^ it 

 would be as well to state once for all that the trunk has no 

 nephridia and possesses no normal openings till after the 

 metamorphosis" (12). 



There is much less agreement concerning tlio cavities in 



