144 IWAJI IKEDA. 



shiplei, for here are two causes promoting similarity, 

 namely, the close specific relationship on one hand, and the 

 similar degenerative processes due to parasitism on the other. 

 The description so far given sufficiently indicates that the 

 present species is a member of the family Bouellidte and is more 

 closely related to the genus Hamingia than to Bon ell i a or 

 Protobonellia. It also plainly indicates that in the present 

 species several important generic characteristics of Hamingia 

 as diagnosed by Danielsen and Koren^ are absent. Thus in 

 the female of Hamingia the ventral hooks and the skin- 

 papillfe are absent, the anal glands are of the ordinary number, 

 or two, and, in the male," the ventral hooks are present. The 

 rest of the generic characteristics of Hamingia, for instance, 

 the shape of the proboscis, the texture of the skin, the number 

 of the oviducts, and the sexual dimorphism, are not peculiar 

 to the genus, since some or nearly all of them may be recog- 

 nised in the genera Bonellia and Protobonellia. Thus 

 compared, it becomes obvious that the present species does 

 not belong to the genus Hamingia. The multiplied con- 

 dition of the anal glands, and the fact that the ventral hooks 

 lack a muscular sheath as well as radial muscles, are certainly 

 two interesting characteristics which accurately distinguish 

 the present species from every known Bonellian Echiuroid 

 except Hamingia ijimai. The latter s})ecies is that with 

 which I made the erroneous generic identification, chiefly 

 owing to having overlooked the presence of the small hooks 

 in the female form. The hooks which are now found in tlie 

 two species in the same condition seem to be stiikingly 

 different from those known in other Echiuroids in one 

 important point, that is, they are in an extremely abnormal, 

 and, very probably, degenerative state of existence. Jn 

 Bonellia miyajimai, which has hitherto represented the 

 single case known of the acanthous abnormality, the abnor- 



' Vide note on p. 138. 



- The male wiis not known to Danielsen and Koren, but was discovered 

 and described by Sir Ray Lankester, ' Ann. and Mag. Nat. Hist.,' 1883, 

 xi, pp. 37-43. 



