134 SOME ASCIDIANS FROM THE ISLE OF WIGHT. 



considerable reduction since their capture. In the rough notes 

 which I then made, I put down the length as " about 5 inches/^ 

 while actual measurement now shows that the largest of the two 

 brought away does not exceed 3 inches. Allowing for a possible 

 degree of error in my original estimate of their size, there must 

 still, I think, have taken place some contraction of their test and 

 body in the four months during which they have been in alcohol. 

 It is, I admit, unsafe to argue upon these grounds, for the larger 

 ones may have been just those which I dissected at the time of 

 capture and did not retain. I will, therefore, merely state that the 

 size of some of the specimens which I found was fully 4 inches. 



The colour of the individuals when alive was hardly different 

 from that which these spirit specimens now exhibit. It is sufficient 

 to say that there was an almost total absence of red pigment in 

 their bodies, and what did exist was confined to the region of the 

 siphons, particularly the oral siphon. The test-vessels, also, with 

 their terminal dilatations, were destitute of red and of all conspicu- 

 ous colouration. 



The species Ascidia mentula has been described in greatest detail 

 upon Mediterranean specimens, although it is widely distributed 

 round all the coasts of Europe, and has been called the commonest 

 of the British deep-water Ascidians. Off the south-western shores 

 of England, however, it is certainly not common within the 40 

 fathom line ; I have only taken it once or twice there, and its place 

 seems to be occupied by two other large Ascidians, Phallusia 

 mammillata and a coarse variety of Ascidiella aspersa. Indeed, the 

 fact that there is extant no anatomical description of British 

 specimens referred to Miiller's species, seems at first to be strange, 

 if they are really so abundant. 



A comparison of my specimens with Miiller's original description 

 revealed some distinctions which at the outset seemed to be of some 

 importance. Both of Miiller's specimens were brilliantly pigmented, 

 the whole of the body within the test being of a bright crimson 

 colour, except over the area occupied by the viscera on the left side, 

 which was whitish, the intestine being of a livid green colour 

 {" colorem luridum exhibens "). 



But in Traustedt^s specimens from Naples the red pigment was 

 found to be a very variable and unreliable characteristic ; sometimes 

 the stomach only was so coloured, sometimes this pigment was 

 spread over the entire area of the branchial sac (as in Miiller's 

 specimens), whilst sometimes individuals were taken which were 

 quite destitute of red colouration. 



Roule, at Marseille, has observed that the test is almost always 



