432 DR S. F. HARMER AND DR W. G. RIDEWOOD ON THE 



proboscis is not only a very mobile organ, but is evidently also capable of considerable 

 change in superficial extent ; a large proboscis on a bud with three pairs of arms is 

 thinner than a smaller proboscis on another bud with the same number of arms. 



In buds with three, four, or five pairs of arms the first portion of the gut can be 

 seen in the interior of the " body " in clarified preparations ; it appears as a caecal tube, 

 connected with the mouth, and with a slender cord passing from the blind extremity 

 towards the stalk. The state of preservation of the material is so poor that the study 

 of the internal structure of the buds by means of serial sections did not seem advisable. 

 The development of the internal organs in buds of Cephalodiscus is not likely to differ 

 much among the various species, and any time and energy spent upon a study of these 

 parts is most profitably expended by restricting oneself to material that is specially 

 suited to the methods of microscopical technique. 



On comparing the buds of C. agglutinans with those of other species of Cephalo- 

 discus, one is struck by the fact that in the relatively late appearance of the arms this 

 species more closely resembles C. gilchristi, a species of the subgenus Idiothecia, than 

 it resembles species of the subgenus Demiothecia, such as C. dodecalophus and C. 

 hodgsoni (RIDEWOOD, 07 2 , pp. 231 and 225). Incidentally it may be mentioned that the 

 buds of C. sequatus and C. insequatus, examined by us in material collected on the 

 Swedish South-Polar Expedition, agree very closely with those of C. dodecalophus and 

 C. hodgsoni. In C, dodecalophus, C. hodgsoni, C. insequatus (which we regard as 

 synonymous with C. hodgsoni, see p. 4:6), and C. sequatus the first pair of arms reach 

 the end of the proboscis at a stage when three pairs of arms are recognisable (07 2 , p. 231, 

 text-fig. 4, G and H, and p. 225, text-fig. 2, G) ; whereas in C. agglutinans, as also 

 in C. nigrescens and C. gilchristi (07 2 , pp. 236 and 243), the arms at the three-pair 

 stage (text-fig. 5, D) are but insignificant bead-like outgrowths from the sides of the 

 collar, and are very remote from the edge of the proboscis. 



SYSTEMATIC POSITION OF C. AGGLUTINANS. 



We have not found it an easy matter to come to a definite conclusion with regard 

 to the affinities of the Scotia species of Cephalodiscus. In the present state of our 

 knowledge it is probably best to accept provisionally the subdivision of the genus into 

 the three subgenera mentioned on p. 408. We may remark, however, in passing that 

 it is surprising that a crowd of independent zooids should be able to build up a 

 coanoecium, by their united efforts, which has a definite character of its own. But, on 

 the other hand, there is sufficient resemblance between the ccenoecia of C. levinseni, 

 C. nigrescens, and C. gilchristi to justify their inclusion in a single subgenus, Idio- 

 thecia ; and this becomes the more significant when it is remembered that these species 

 have been recorded from such widely distant localities as between Japan and Corea, 

 the Antarctic Ocean, and South Africa respectively. There is, moreover, a considerable 

 amount of resemblance in anatomical structure between the zooids of species which 



(ROY. 8OC. EDIN. TRANS., VOL. XLIX., 556.) 



