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



is completely cut off from its neighbours (compare the septa in C. nigrescens, RIDEWOOD, 

 07 1 , pi. iv. fig. 10). 



The single short spine or lip at the side of each ostium in C. agglutinans finds a 

 parallel in C. (I.) nigrescens, C. (I.) levinseni, and C. (0.) solidus. In C. (1. ) gilchristi 

 there are long spines, about as numerous as the ostia, but not very distinctly related 

 to them ; whereas in C. (I.) indicus, C. (O.) densus, and C. (0.) rarus there are no 

 lips to the tubes. In C. (D.) dodecalophus, C. (D.) hodgsoni, and C. (D.) lequatus, 

 however, the spines are long and numerous, usually four or five to each ostium. 



The study of the zooids may be held to give some support to the view that the 

 nearest ally of C. agglutinans is to be found in the subgenus Idiothecia. There is 

 considerable resemblance between the zooids of C. agglutinans and C. nigrescens in 

 their relatively large size, in the general proportions of the body, in the large number 

 of arms, and in the dense pigmentation of the skin. Too much weight, however, must 

 not be attached to this last character, since the pigmentation may not really be an 

 indication of affinity, but may be of a purely physiological nature, as seems to be the 

 case in certain deep-water pelagic Fishes.* C. sibogse, a species of Demiothecia, has, 

 moreover, a deeply pigmented epidermis (HARMER, 05, p. 8). 



In the absence of end-bulbs with refractive beads at the ends of the arms, C. agglu- 

 tinans agrees with the species of Idiothecia and Orthoecus, and differs from those of 

 Demiothecia. 



Attention has already been drawn (p. 432) to the fact that, in the relatively late 

 appearance of the arms in the buds of C. agglutinans, this species more closely resembles 

 C. gilchristi and C. nigrescens than species of Demiothecia such as C. dodecatyihus, 

 C. hodgsoni, and C. sequatus. 



The special characters of the coanoecium of C. agglutinans might be taken to justify 

 the institution of a new subgenus for the reception of this species. We think it un- 

 necessary to adopt this course ; but it is obvious that, if the species is rightly referred 

 to Idiothecia, the original diagnosis of that subgenus (KlDEWOOD, 07 1 , p. 10) must 

 be amended by adding to the statement, "tubular cavity . . . having no connection 

 with the other cavities of the tubarium," some statement to the effect that the 

 tubes may be connected with one another. The following amended diagnosis is 

 suggested : 



Subgenus Idiothecia. Each ostium leading into a long tube lodged in a common 

 coenoecial substance ; the tubes definitely arranged at a more or less constant angle to 

 the surface, usually completely separated from one another, and each containing a single 

 zooid with its buds, but sometimes connected with one another by an intercommuni- 

 cating system of tubes. 



It may be pointed out in conclusion that the name Idiothecia would not be 

 less strictly applicable in consequence of the extension of the scope of the subgenus, 



* G}. Sir JOHN MURRAY and J. HJORT, The Depths of the Ocean, London (Macmillan & Co.), 1912, pp. 618, 624, 

 677, and elsewhere. 



(ROT. soc. EDIN. TRANS., VOL. XLIX., 558.) 



