368 Copepoda living as Messmates with Ascidians. [Sess. 



the peculiar position of the fifth pair of thoracic feet in the 

 female. This pair, each of which consists of a single, elon- 

 gated, one-jointed branch, instead of being, like the preceding 

 pairs, situated on the ventral aspect of the thorax, are each 

 inserted on the fifth thoracic segment — one on each side, 

 well round towards the dorsal surface — and project outwards 

 in the form of prominent spine-like appendages. The ovisacs 

 are external and contiguous, and together form a globular 

 mass, which is situated on the dorsal aspect of the last 

 thoracic segment, and between the two fifth feet.^ It is 

 fairly evident, from the peculiar and abnormal position occu- 

 pied by the fifth pair of feet, that this remarkable arrange- 

 ment has been brought about so that these appendages could 

 protect the globular ovisac and hold it between them in its 

 proper position, when otherwise it would have been easily 

 displaced. 



The few specimens I have obtained, and which I have 

 doubtfully ascribed to Hesse's species B. riiber, were found 

 in specimens of a Botryllus dredged in the Moray Firth, and 

 also in Loch Fyne. 



Genus Enterocola P. J. van Beneden. 



Specimens of an Enterocola which I have doubtfully re- 

 ferred to E. fidgens van Beneden have on two occasions been 

 dredged in the Firth of Clyde. They were found in the 

 digestive canal (not the branchial cavity) of small Ascidians, 

 the name of which I failed to obtain. All the specimens 

 observed were females, and only one Copepod was noticed 

 in each single Ascidian. The specimen seemed to occupy, 

 to its full extent, that part of the canal where it occurred, 

 and it was therefore somewhat difficult to remove the Cope- 

 pod without displacing one or both ovisacs. The ovisacs, 



^ In the ' Nineteenth Annual Report of the Fishery Board for Scotland, ' 

 Pt. III., p. 242, pi. xvii. , figs. 15-27, I give a description and drawings of a 

 female and a male. The female figure shows the relative positions of the fifth 

 pair of feet and the globular ovisac. Hesse's figures of BotryUophilus ruber, 

 while agreeing generally with the Moray Firth and Loch Fyne specimeos, show 

 the two ovisacs widely apart, one under each fifth foot, — thus presenting 

 an arrangement that apparently has not been hitherto observed by any other 

 author. 



