20 



C. gracilis. (PI. I, figs. 4, 7. PI. III, fig. 22). 



This species differs from the two preceding in the Rhabdopleura-\\V^ slenderness of its 

 stalk and in the profusion with which it produces buds (fig. 4). The stalk is, moreover, nearly 

 alvvays carried in what may be regarded as its primitive position, forming a continuation of the 

 principal axis of the body. 



Fig. 7 shews a side view of a zooid of this species, with rather unusually short stalk, 

 and only a single bud. Fig. 4 represents a mass of buds and young blastozooids, of a kind 

 commonly found in the cavity of the coenoecium of this species. 



C. gracilis normally possesses five pairs of arms. End-bulbs, hearing refringent vesicles, 

 are present in the first pair of arms at least, and sometimes in the second and third pairs, in 

 the buds (figs. 30, 32). They may persist in the adult, but they appear to be sometimes absent. 



C. sibogae. (PI. I, fig. 3. PI. VU, figs. 72—76). 



My examination of this species has been interfered with by the failure of the spirit to 

 penetrate satisfactorily into the deep hing cavities of the basal coenoecium containing the zooids. 

 But in spite of this drawback, some of the main facts appear to be beyond dispute. 



The colony is remarkable for an extraordinary dimorphism of the zooids. The coenoecium 

 contains (I) neuter individuals, of the normal Cephalodiscns type, but usually without reproductive 

 organs (which are, however, indicated in their young condition, while they are still immature 

 buds); (II) male individuals, of an entirely peculiar character. 



(I) Neuter s. 



These resemble the female individuals of C. gracilis in many respects, notably in the 

 slenderness of the stalk. One of them is shewn in fig. 3, in which, however, only a portion 

 of the excessively long stalk is present. They appear to dift'er from the zooids of C. gracilis 

 in the following respects, in addition of course to the sexual difference : 



[o) The proboscis is smaller, in C. sibogae. 



{b) There are four pairs of arms, in which I have not observed vesicle-bearing end-bulbs. 



(c) The greater part of the zooid is extremely dark in colour (almost black), in old individuals, 

 owing to the presence of an unusually large quantity of pigment in the epidermis. 



(flf) The body is more elongated; and in old zooids may be extremely elongated. 



(é) The stalk originates nearer the aboral end of the body. It is extremely long (many times 

 the length of the body) and is indeed so long that I have not succeeded is disentangling 

 the masses of stalks sufficientlv well to tracé the full length of an individual stalk. 



(ƒ) The operculum is larger, although this can only be seen satisfactorily in sections. 



(II) Mal es. 



I reserve a fuller account of these extraordinary individuals for a later part of this 

 Report (Sect. XV). The full grown male (figs. 75, 76) possesses a typical proboscis, with the 

 usual pigment-band. The coUar is not produced into an operculum and bears only a single 



