REPORT ON THE TUNIOATA OP PLYMOUTH. 59 



delay its production. It is now very satisfactory to be assured that 

 the preparation of the Monograph is in the hands of the experienced 

 author of the Reports on the " Challenger " Tunicata. In the mean- 

 time a more or less detailed account of the forms with which I have 

 met at Plymouth may be of some service as a contribution towards an 

 improved knowledge of the British representatives of the group. 



In the neighbourhood of Plymouth I found the rocks under the 

 Hoe, the north and east sides of Drake's Island, the wooden piles of 

 the docks and wharves in Millbay and the Cattewater, the rocks and 

 tidal pools of the Mewstone and Wembury Bay, to be all good 

 hunting-grounds for the littoral species of composite Tunicata ; the 

 best dredging-grounds for Ascidians generally were undoubtedly the 

 neighbourhood of the Duke Rock, the Queen's Grounds, and the 

 deeper waters off the Eddystone, the Mewstone, and Bigbury Bay, 

 while some forms were most common upon Zostera in Cawsand Bay ; 

 but it was almost impossible to use any of the ordinary methods of 

 collecting within Plymouth Sound without obtaining numbers of 

 Ascidians of various species. Very few simple Ascidians were to be 

 found inhabiting the tidal zone ; they were most plentiful in the deep 

 water of the trawling grounds, on the rough ground off the Mewstone. 

 In reporting upon the Ascidians of Plymouth, I have taken 

 Clavelina and its allies as my starting point, since this genus includes 

 the forms which are in many respects probably the least modified 

 descendants of the earliest Ascidiacea. But I am met at the outset 

 by the problem which is now engaging the attention of every 

 Ascidiologist : What taxonomical value must be attributed to the 

 possession of the power of budding and of the formation of colonies ? 

 A full discussion of this question I cannot give here, but since the 

 matter bears directly upon the classification which I shall employ, I 

 am bound to admit that the division of the Ascidiacea into the sub- 

 orders Ascidice simplices, Ascidice compositce, and Ascidice salpiformes 

 so completely disregards the admitted inter-relationship between 

 various sections of these groups, that its adoption seems to me to 

 involve the rejection of any morphological, and therefore genetic, 

 meaning in classification altogether. The term " composite Asci- 

 dians" is in practice a very convenient one, but this is not a 

 sufficient reason for retaining it as the symbol of a natural group, 



