BRYOZOA 21 



Bugula bicornis Busk. 



(PI. I, figs. ±a-k) 

 Bugula licorjiis Busk, Zool. Chall. Exp., vol. X, pt. XXX. p. 40. pi. IX, fig. 1. 



In the Antarctic spécimens there is a structure not mentioned in the « Challenger 

 Report », for from the main branches formed of long zoœcia there anse, at the distal end of 

 the zoœcia, from the dorsal surface of the free terminations, branches formed of much smaller 

 zoœcia, and as far as I hâve seen, thèse short celled branches never divide or give off 

 fresh branches. As a rule thèse growths do not exceed six or seven zoœcia, but exceptionally 

 may reach to twenty. Thèse short zoœcia are only attached to one another by two latéral 

 rosette plates near the base, while the distal end is free. The long zoœcia hâve about four 

 latéral rosette plates, and the first short zoœcium is attached at the proximal end, by one 

 rosette plate to the long zoœcium of the main branch (fig. 4, b. r.). 



The finest spécimen, from 608 growing on Rctepora, forms a kind of mat with the 

 branches growing in ail directions, and reaching to a width of about 5o millimètres. 



The radicles are attached to neighbouring branches, as in B. reticulata B., but this 

 of course cannot be compared with the Connecting tubes of Canda arachnoïdes, &c. A pair 

 of vermiform bodies arise from the front wall of the zoœcium, and thèse are most distinct 

 in zoœcia which are otherwise quite empty, or only contain a « brown body », though thev 

 can be found in zoœcia having an active polypide. Although assuming a différent form 

 this is undoubtedly the équivalent of the gland-like body to which I hâve frequently referred. 

 They commence as small almost globular bodies, but ma}- attain to nearly the length of a 

 zoœcium ; and also in Bugula reticulata, var. Spinoza nov. small globular bodies are seen, 

 but none of an elongate form hâve been found. 



In the latéral branches, with short zoœcia, there seems usually to be only one small 

 avicularium to a zoœcium, though occasionally there is one large one nearer to the proximal 

 end, but while there is a différence in size the shape is similar. 



Besides the strong muscles, for closing the mandibles, there are a row of muscles 

 round the proximal edge of the avicularium (see PI. I, fig. 4^). Thèse are similar to the 

 muscles which I hâve previously figured in the mandible of Bcania mageltanica Busk (') 

 (PI. II, figs. 14, i5) and in this memoir in PI. Mil, figs. ja, b ; and this is a point of 

 very great interest, as, apparently, thèse muscles are homologous with those of the compensation 

 sac of the zoœcia. 



There are 23-25 tentacles. Busk says 18-20 but probably thèse figures are not taken 

 from sections, and but little reliance can be placed upon the counting of tentacles unless 

 sections are eut. 



Bugula avicularis has 14-15 tentacles (H.), 14 (Bexed.), i3-i5 (Calvet) ; B. flabellata 

 Thomps. has 16 (W.), 14 (H.); B. Murrayana Johnst., 18-21; var. fruticosa Pack., 17; B. plumosa 

 Pall., ii-i3 tentacles; B. spicata H., 16; B. turbinata Aider, 16; B. purpurotincta Xorm., 14 (Sars), 

 16-18 (Daly.) ; B. ncntina L., 23 (Calvet); B. calathus Xorm., i5 (Calvet); B. Sabatieri 

 Calvet 12-14 (Calvet) ; B. reticulata B., 21-22 (W.) ; B. bicornis Busk, 23-25 (W.). 



(1) On Bryozoa from Rapallo, &c. [Linn. Soc. Journ. Zool., vol. XXVI, pi. II, figs. 14, i5.) 



