THE HISTORY OF BALANOGLOSSUS AND TORNA.RIA. " 435 



be compared to the gills of Balanoglossus, but like other gill-like organs in Annelid 

 they connect with the perivisceral cavity. Tomopteris has, however, several feature- 

 which had led Claparede to regard it as intermediate between the Annelids proper 

 and Nemertians: the absence of well-defined articulations and of set;e along the lat- 

 eral appendages of the body, the setaB being limited to the cephalic appendages. We 

 must, I think, look upon Balanoglossus as the type of a family intermediate between 

 Tubicolous Annelids and Nemertians, to which its mode of development is closely 

 analogous, while its structural features recall more strongly those of several families 

 of Tubicolous Annelids. We have among Sabellidae genera in which we find a most 

 . rudimentary proboscis immediately above the opening of the mouth, on the dorsal 

 side, under the collar ; as, for instance, the genus Artacama of Malmgren. 1 Then 

 we have such forms as Myriochile, Malm., 2 where we find the first trace of a collar 

 totally destitute of cephalic appendages of any sort, these taken in connection with 

 such genera as Sabellaria, where the development of the posterior part is great, and 

 independent, as it were, of that of the anterior part of the body, where we have 

 a collar, gills, and dorsal cirri, as well as setae, with all the intermediate passages 

 afforded by the Maldaniae, Terebellidae, Sabellidae, Hermellidae, show us many fea- 

 tures which are dimly recognized in Balanoglossus, and which link together families 

 thus far as disconnected as the Nemertians and Tubicolous Annelids, — an association 

 which the great similarity between the Loven type of Annelid larva and the larva) of 

 Nereis and Phyllodoce shows not to be so far-fetched as might at first be imagined ; 

 hinting at a more intimate relationship between the different orders of Annelids than 

 had thus far been recognized. It must, however, not be forgotten that the peculiar 

 structure of the proboscis, with its openings and diverticula from the alimentary 

 canal, are features thus far not known except among Nemertians. The lateral cephalic 

 splits of some of the Nemertian genera correspond with the openings formed by the 

 attachment of the proboscis, for its whole length, to the base of the collar, and their 

 articulations are quite as distinct as in some of the Annelids. It may be that future 

 investigations may give a different explanation of the skeleton supports of the base of 

 the proboscis and of the gills, which would homologize them in part with the probos- 

 cidal armature of some Nemertians. Keferstein has described something analogous to 

 the ciliated furrows of Balanoglossus in some of the Nemertians, where the lateral part 

 of the intestine forms pouches re-entering towards the dorsal part, this being the rudi- 



mentary structure of what 



]y developed in Balano 



Van Bene 



1 Malmgren, A. Nordiska Hafs Annulater, PI. XXIII. f. 60. 

 * Malmgren, A. Annul. Polychaeta, 1867, p. 101. PI. VII. f. 7. 



