PTEROBRANCHIA OF TEE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 411 



unnecessary. Most of the pieces of material show no branching, but resemble the 

 piece of which a photographic reproduction is shown in text-fig. 1, A. 



The surface of the colony appears rough, and, if the ostia or openings of the tubes 

 are not clearly visible, does not differ much from the surface presented when a piece 

 is broken across (text-fig. 1, D and E). But in sheltered situations, as between the 

 branches of a piece of colony, such as is shown in PI. I. figs. 1, 4, there are blunt 



A 



B 



D 



m 



TEXT-FIG. ]. Photographic reproduction of pieces of colony of C. agglutinans ; of the natural size. A, a piece broader at 

 the free end (uppermost in the figure) than at the basal end, showing no branches ; B, a piece showing a branching into 

 two ; C, a longitudinal median section of a piece of colony ; D and E, transverse sections through a piece of colony. The 

 darker areas are the tubular spaces occupied by the zooids, the white specks are small pieces of shell included in the 

 coanoecial substance. 



brownish processes or "spines" projecting to an extent of 3 mm. beyond the general 

 surface. Inspection shows that these are really the projecting lips of the inhabited 

 tubes, one to each tube, similar to the lips that occur on the surface of a piece of 

 C. nigrescens (07, pi. iv. fig. 11 ), but differing in being less regular in form. These spines 

 are built up by the superposition of solid caps of coenoecial substance upon the summit 

 of pre-existing spines, just as are the long spines of species of Cephalodiscus such as 

 C. dodecalophus, C. hodgsoni (07, pi. iv. fig. 21), and C. gilchristi (06, pi. iii. figs. 9, 

 10, 11), but they differ in not exceeding a length of 3 mm., and in being restricted in 



(ROY. soc. EDIN. TRAXS., VOL. XLIX., 535.) 



