STRUCTURE OF THE MARINE POLTZOA. 5 



organs. Each carries on its summit a bunch of immovable setae. 

 The cavity of the tubercle is filled by the pyriform nerve-knot, 

 which thus lies just under the surface of the integument, and is 

 in contact with the bases of the setaa. Salensky compares these 

 organs with the setigerous calcar of the Eotifera, and points to a 

 close correspondence of structure between tlie two. 



Nearly simultaneously with Salensky, and quite independently, 

 Vogt* describes another previously unnoticed species oiLoxosoma. 

 It occurs parasitically in small tufts on the caudal extremity of 

 two species of Phascolosoma, a genus of worms, and is hence named 

 by its discoverer Loccosoma phascolosomatum. 



The oblique direction of the cup-like body by which all the 

 species of Loccosoma are distinguished, has suggested to Vogt a 

 comparison to the hood of a cloak tied in front by a string. The 

 space within the hood he names the vestibule ; it contains the 

 mouth, anus, and place of exit of the generative organs. 



The peduncular gland observed in certain other species of Loxo- 

 soma is altogether absent in the adult state of L. phascolosomatum, 

 though it exists in the larva. Vogt further describes setigerous 

 papilla? which he regards as organs of sense. Unlike the similar 

 organs described by Salensky, these are only two in number, one 

 on each side of the body. Vogt, however, has failed in his attempts 

 to find any trace of a central nervous system. 



The mouth, which, in the form of a very wide funnel, opens into 

 the vestibule at the base of the tentacular crown, is provided with 

 two projecting lips, one a button-shaped prominence on the ven- 

 tral side, the other, longer and hook -shaped, on the dorsal, where 

 it projects into the vestibule. 



Vogt has convinced himself that L. phascolosomatum is dioecious. 

 He describes in the male a thick-walled sac, which lies in the 

 mesial line over the stomach, and which becomes filled with sper- 

 matozoa. This communicates, by two very short canals, with two 

 gland-like organs, wbich are situated one on each side of the 

 stomach, and which he regards as testes, in whose cells the sper- 

 matozoa are generated before passing into the median seminal re- 

 ceptacle. He has seen the spermatozoa expelled from this recep- 

 tacle into the cavity of the vestibule, and has noticed them esca- 

 ping thence into the surrounding water. 



* Carl Vogt, " Sur le Loxosome des Phascolosomes," Archives cle Zoologie ex- 

 perimentale, 1877. See also a translation and condensation of that memoir by 

 Hincks in Quart. Journ. Micr. Sc. vol. xvii. new series. 



