1906-1907-] Copepoda living as Messmates with Ascidians. 367 



those examined the abdomen is bent downwards, and forms 

 a considerable angle with the thorax. The furcal joints are 

 very short, and armed with hooked spines ; the limbs are also 

 short ; while the ovigerous pouch, though of moderate length, 

 is but slightly dilated. I found this species fairly common 

 in large Ascidians dredged in Scapa Flow, Orkney, and I have 

 also collected it in Loch Fyne. The Eev. A. M. Norman 

 records it from the branchial sac and water-passages of Ascidia 

 mentula collected at Shetland and Oban. 



Genus AsciDicoLA Thorell. 



Ascidicola rosea Thorell is the only described species, and, 

 like Botachus cylindratus, is elongated and slender, and might 

 at a casual glance be mistaken for that species. But besides 

 being at least twice as long as Botachus, A. rosea is furnished 

 with two external ovisacs on the posterio- dorsal aspect of the 

 thorax.^ These ovisacs are at first contiguous, but later when 

 the eggs have developed the ovisacs may become divaricate, as 

 exemplified by some of the specimens now exhibited. I have 

 obtained this species in Ascidians from Scapa Flow, Loch 

 Fyne, and the Firth of Forth, but always sparingly. The 

 Eev. A. M. Norman has found it in Ascidia sordida from 

 Shetland, and in Ascidia mentula dredged at Oban and at 

 Birterbuy Bay, Ireland, while Dr Brady has dredged it off the 

 coast of Durham, Dr Brady gives the length of Ascidicola 

 rosea as 5 mm., but those I have from Scapa Flow scarcely 

 reach 4 mm. in length. 



Gem(,s BoTRYLLOPHiLUS Hesse. 



Several species of Botryllophilus have been described, but 

 they may not be all distinct. They all appear to be some- 

 what rare, but that may be more apparent than real, for they 

 are small species, and usually occur in the smaller Tunicates, 

 such as Botryllvs sp., Distoma, &c., which are more trouble- 

 some to examine than the larger Ascidians. The Botryllo- 

 phili are readily distinguished from other Notodelphyoida by 



' " Les ceufs pondus en sacs ovigeres exterues, sans abri dans cavite incuba- 

 trice close." — 'Les Copepodes du Boulonnais,' p. 208. 



