75 



It is very doubtful whether Bcsk's species was correctly placed in Farrella l ), which is 

 characterised, according to the diagnosis given by Hincks 2 ), by having a bilabiate orifice. 

 F. repens is said by the same author to have 10 — 12 tentacles. 



From V. uva the present species seems to be separated by the mode of origin of the 

 zooecia. The arrangement is both characteristic and constant, a single zooecium or a pair of 

 zooecia being developed at the distal end of an internode, and ahvays from a minute rounded 

 or slightly pointed structure (figs 5 — 7) which appears to be a vestigial internode. The zooecia 

 may be unilateral or ma} - occur on both sides of the internode, sometimes with the addition 

 of a lateral branch. In V. uva the distal end of the internode may give rise to several zooecia 

 on each side. 



In most of the specimens a considerable proportion of the zooecia have assumed the 

 contracted form shown in figs 5, 6. This change, which has not escaped the notice of previous 

 writers (e.g. Waters 3 )), and has already been alluded to in the description of several of the other 

 Ctenostomes recorded in the present Report, is associated with the degeneration of the polypide. 

 The shortened zooecia are usually more or less pear-shaped, but may assume irregular shapes 

 (fig. 6). When fully formed they have no obvious contents except a brown body, or sometimes 

 two of these structures. Fig. 5 shows that a new polypide may be developed in a zooecium 

 which has undergone this change. 



The zooecium contains no definite muscles by which the contraction could be effected; 

 and the occurrence is perhaps due to a loss of turgidity, by the absorption of some of the 

 water contained in the body-cavity. The process is probably aided by the contraction of the 

 cuticle, which may be supposed to be elastic and somewhat stretched in the ordinary condition. 

 The circular markirig of the body-wall which is a characteristic feature of zooecia in this 

 condition is satisfactorily accounted for on this hypothesis. 



The zooecia in their active condition (fig. 7) have a form very different from that of 

 those just described. They are elongated, straight or curved, and are more or less cylindrical, 

 though frequently dikited in their proximal half. They have a very transparent body-wall, which 

 is well stretched and has none of the circular markings of the contracted zooecia. At their 

 proximal end they taper off into a stalk-like portion, which is usually short but in the specimen 

 393. C. (figs 9 — 12) is much elongated. 



The vestibule is relatively short, and the collar is very delicate and small. The tentacles 

 are 8 in number, and are commonly bent at their tips during retraction ; in which condition 

 the oesophagus is folded on the pharynx. There is no gizzard; in which respect the present 

 species agrees with the usual definition of the genus. 



Some of the zooecia (e. g. in 337. B.), of the ordinary, uncontracted form are fertile. 

 The vestibule persists, but the rest of the polypide has atrophied, with the exception of a sac 

 which encloses the embryo and is no doubt the remains of a tentacle-sheath. The embryo is 



1) Farrella Ehrenberg, 1839, Üb. d. Bildung d. Kreidefelsen", Phys. Abhandl. k. Ak. Wiss. Berlin, a. d. Jahre 1838, Table II 

 (= new name for Lagcnclla Karre, 1837, preoccupied by Lagc/itlla Ehrb., 1832). 



2) Hincks, 1880, t. cit., p. 52S. 



3) Waters, A. W., 1910, p. 239. 



75 



