43S PEOr. W. A. HERDMAN ON BETTISH TUNICATA. 



of those ia the bottle seems to me to be Ascidiella venosa ; 

 the others I cannot distinguish from Ascidia mentula. Hancock 

 gives as a character separating this form from A. mentula that it 

 is more extensively attached, " adhering by the whole side ; " but 

 one at least of the type specimens is only slightly attached by 

 the posterior end. The fact is that amongst specimens which I 

 have collected at East Loch Tarbert, and which T at once re- 

 ferred to Hancock's '"'' rubicunda^'' it is easy to find individuals in 

 all conditions of attachment — some are merely clinging slightly 

 by some one point to the edge of a stone or a Laminaria 

 " root," or a piece of broken crockery, others lie flat along, 

 and are attached by the whole surface, or, if in a crevice, even 

 by both surfaces. I need not go over in detail the notes I 

 have taken from Canon Norman's specimens and from my own 

 Tarbert ones. They show a general agreement with A. mentula 

 along with considerable individual variation. (See also below, 

 p. 442.) 



5. A. rohusta, Hnk. — I have examined Canon Norman's type 

 specimens of this from Herm ; but unfortunately some of them 

 are merely empty tests, and the others are in bad condition, so I 

 was imable to make out the characters very satisfactorily. It may 

 be that, as Grarstang suggests, this species is a form of ^. mentula. 

 I have found, amongst the specimens agreeing with Hancock's 

 A. rubicunda from East Loch Tarbert, some growing amongst 

 Laminaria " roots " which agree in external characters with this 

 form. On the other hand, when examining Canon Norman's 

 specimens, I was distinctly reminded by them of Alder's Ascidia 

 depressa ; and some young specimens labelled " from Guernsey, 

 named by Hancock," are very like young A. depressa. These 

 young specimens are also not unlike the specimens of ^.^ro- 

 ducta, Hnk., which I have examined. As Ascidians continue to 

 grow and change in appearance long after they have commenced 

 to reproduce, and so can be sexually mature without being full 

 grown, it is often very difficult to correlate younger and older 

 forms of the same species ; and there must constantly be cases of 

 doubt until the various species have been reared iu aquaria and 

 the same individuals have been drawn at various ages. 



6. A. mollis, Aid. & H. — I have not seen any specimens of this 

 species ; but Mr. Grarstang * has found some at the I^le of "Wight 



* Journ. Mar. Biol. Assoc, n. s. vol. ii. no. 2, p. 119. 



