268 REPORT ON THE PENNATULIDA. 



round the rachis, and wliicli persists comparatively unaltered on the 

 dorsal and ventral surfaces (Fig. G, liii), portions the direction of 

 which has become changed by the pittings in of the surface which 

 form the stomach-cavities of the polypes. 



Fi'om the mode of formation of the body-cavities of the polypes out 

 of parts of the canal system of the rachis, it is clear that the continuity 

 between these two systems which we have seen persists in the adult 

 is a primitive otie, and not a secondary one acquired in the course of 

 development. 



5. — Anatomi/ of the Zooich. — 



The zooids of Virgularia are simply arrested polypes, polypes which 

 have stopped short at the stage of development represented in Fig. 6. 

 They have no tentacles ; their stomach-cavities are merely blind 

 sacs, the walls of which are not thrown into folds ; and, in fact, they 

 resemble these rudimentary polypes in all points except in having no 

 reproductive organs developed in connection with them. 



6. — Zoological Position and Affinities. — 



The position of Virgularia relatively to the other two genera is 

 shown in the table on page 1 of this report. The generic characters, 

 as stated by Kolliker,* are as follows : — 



" Genus : Virgulariu. Leaves small, attached to the rachis by 

 wide bases, ending below in a long series of undeveloped leaves. 

 Polype cells fused together along the greater part of their length, 

 either in a single row, or else alternating so as to give the appearance 

 of two rows. Tentacles cylindrical, with short pinnules. Reproductive 

 organs, as a rule, contained within the rachis at its lower end, and 

 only in a single species found in all the leaves. Zooids lateral, in 

 single or multiple rows between each pair of leaves. Radial canals in 

 two longitudinal ridges along the ventral side of the rachis. A terminal 

 dilatation at the end of the stalk. Stems cylindrical. Calcareous 

 spicules absent in the rachis, but present in some cases in the stalk in 

 small uumbei's." 



Of the nine species of this genus distinguished by Kolliker the 

 descriptions of five are based on the examination of single specimens 

 only ; and of the remaining four there is no doubt whatever that the 

 one to which the Oban specimens are to be referred is the typical 

 species of the genus, I', viirabilis, the definition of which is as follows : — 



V. mi rah His. j "Whole colony up to fourteen inches in length; 

 feather two and a half to three times the length of the stalk ; leaves 

 half-moon shaped, smooth, placed laterally but slightly obliquely, the 

 ventral border being higher than the dorsal, overlapping one another 

 only slightly or not at all, attached by wide bases. Polypes six to 

 nine in each leaf, their cavities distinctly separated from one another. 

 Zooids lateral, in one or two rows. Reproductive organs only developed 



Kiilliker, " Alcyonarieii," p. 182-3. i Ihid., p. 190. 



