636 PROFESSOR E. RAY LANKESTER. 



terminate in a fully-formed polypide, in which case we should 

 be able to trace the gymnocaulus of the colony back to the first 

 septum of the tubarium, where its character would be found to 

 suddenly change, and beyond the septum it would be shrunken 

 and invested with a caulotheca and converted into pectocaulus. 



Supposing the branch to be a still-growing " proliferous 

 branchj" as was the case with most of the branches at 

 the season of the year (August) when my specimens were 

 obtained, we find that the tubarium of the branch-axis does 

 not terminate in an upstanding polypide-tube, but is recumbent 

 and fixed to the supporting surface up to its termination, 

 which is not ring-like, but deeply notched (fig. 1, a, PI. 

 XXXIX). The terminal polypide is immature, having a very 

 remarkable appearance. The buccal-disc is relatively of very 

 great size, elongated in shape, and distinctly bifid. It is 

 engaged in actively secreting the obliquely notched segments 

 of the tubarium, the form of which depends on the form of the 

 bifid buccal-disc. Placed superiorly to the elongated buccal- 

 disc are the rudiments of the two lophophoral arms. The 

 polypide-stalk (gymnocaulus) follows close upon the elongated 

 buccal-disc. It is not possible in this phase of the development 

 of the polypide to distinguish thorax and abdomen. The 

 polypide-stalk can be traced in the form of gymnocaulus as far 

 as a first transverse septum which is placed as a diaphragm 

 across the tubarium (fig. 3, PI. XXXIX) ; sometimes it may 

 be traced through and beyond the first such septum to a 

 second (fig. 1, PI. XXXIX). Beyond either the first or second 

 transverse septum the gymnocaulus shows evidence of the 

 formation of a heavy cuticle on its surface, and a little further 

 back it is quite black (see for three stages of cuticularisation 

 of the caulus figs. 3, 4, 5, PI. XLI). 



The naked still-contractile part of the polypide-stalk shows 

 one or more protuberances on its surface, which are very young 

 buds. The youngest is that nearest the terminal 

 polypide, which is itself in a rudimentary state. As we pass 

 backwards along the stalk we find a series of buds, each one 

 older than that in front of it, until we arrive at fully formed 



