644 PROFESSOE E. RAY LANKESTER. 



caulus " and become " hardened stalk " or " pectocaulus." e. Third bud : 

 it has reached the stage when it must force its way through the wall of the 

 axial tubarium, and is commencing to construct a lateral polypide tube (e e) 

 for itself, ring by ring, e e. The commencement of the polypide tube of the 

 polypide e. f. The fourth bud in age, reckoning back from the youngest. It 

 has reached the condition of a fully-grown polypide, and has constructed a 

 complete polypide tube with recumbent and vertical (.r) portions, g, h, i, k. 

 The fifth, sixth, seventh, and eighth polypides, budded from this axis. Between 

 /and^, however, a proliferous bud has developed, giving rise to the branch 

 z. The forking of the pectocaulus is hidden here by the stalk of the polypide^. 

 I. Stalk of the proliferous polypide which terminates the branch a, and is at 

 this point still in the condition of " gymnocaulus," or " soft stalk." m. Older 

 portion of the stalk, in which the formation of a cuticular investment is com- 

 mencing. 7i. Still older portion of the stalk, now in the condition of " pecto- 

 caulus" or "hard stalk," enclosed in a thick brown cuticular tube, and fixed 

 to the floor of the tubarium. o. Small pedicle of pectocaulus supporting 

 lateral polypides. p^iojfi. Successively-formed septa, dividing the axial 

 portion of the tubarium into a series of chambers, corresponding in age to 

 the series of polypides the most recent being p^ and the oldest p^. q. Buccal- 

 disc of immature polypide, usually showing bilobate form. r. Tentaculiferous 

 or lophophor-arms of polypide buds. s. Polypide stalk of buds, s s. Polypide 

 stalk (gymnocaulus) of complete polypide. L Tentaculiferous arms of complete 

 polypide. u. Buccal-disc of complete polypide. w. Abdomen of complete poly- 

 pide. .T. Point at which the polypide tube ceases to be recumbent and fixed to 

 its support (the Ascidian test, a dead shell or corallum), and commences to b^^d 

 upwards towards the vertical position, y. The vertical portion of the polypide 

 tube. z. Branch which is given off between the septa p^ and p^, and equally 

 with the branch a, is a continuation of the axis which bifurcates to form them. 



Pig. 2. — Portion of the tubarium of B.habdopleuraNormani, which 

 has grown in the form of a coil and contains six oval buds of an exceptional 

 form. a. Pectocaulus. b. Gymnocaulus. c. Normal bud. d. The six 

 peculiar buds, some apparently detached from the gymnocaulus. 



Fig. 3.— Outline sketch of a proliferous branch of a colony of Rh. 

 Normani, in order to show the form and size of the successive buds. The 

 buds are numbered in order of age, No. 1 being the youngest. The leading 

 bud or immature polypide is, although less advanced in development, older 

 than any bud carried by the branch, older therefore than No. 7 ; as also in 

 Fig. 1, the leading bud of the branch a is older than the fully-formed poly- 

 pide/, which is the last on its branch. Letters as in Fig. 1. 



Fig. 4.— Portion of a polypide's tube, to show the way in which the com- 

 ponent rings interlock. 



Fig. 5.— Portion of the axial tubarium, to show internal upgrowths a a, 

 which form an incomplete tube within the tubarium, overlying the pectocaulus. 



