222 DE. W. B. BENHAM OlS^ 



to a certain degree appears to have misunderstood the relative 

 value which I set upon these " specific characters." 



In writing of P. capensis (p. 229) he refers to two new 

 " species," P. seccta and P. Willeyi, which I founded, but which 

 I pointed out differed but very slightly from P. capensis and 

 P. operculata. Micha,elsen, rightly I think, now unites these 

 and certain other " species " with P. capensis, but I see little 

 need for the formation of " subspecies." If they are sufiiciently 

 distinct, it seems to me that the term species is as good as a 

 subspecies ; and seeing that P. sexta and P. Willeyi were each 

 founded on one specimen, I should go further than Michaelsen 

 and leave out " subspecies." I suggested (p. 46) that possibly 

 P. sexta was a "hybrid" or an abnormal specimen. As Mi- 

 chaelsen has had a greater abundance of material he is in a 

 better position than I was to determine the matter, and the 

 names I used for these two worms must be dropped. 



Now, with regard to Michaelsen's criticism of the " specific 

 characters." He takes them, one by one, and shows that each 

 may vary. This, no doubt, is true; but I never intended that any 

 one of these characters hy itself \^ sufficient to diagnose a species. 

 I merely wished to insist upon special attention being paid to all 

 these points, hecause they do vary ; and until more trouble is 

 expended on an accurate description of each presumed " new 

 species " we shall not be in a position to decide whether it is or 

 is not a mere variation. 



I agree with him fully that colour, or size, or number of 

 segments, and so on, onust he taken loith certain anatomical 

 characters. He points out that colour is no safe guide since it 

 is variable ; it may fade on being affected by the discoloration o£ 

 the spirit by the cork. Quite so. On p. 42 I wrote "no doubt 

 the colours will soon fade in spirit," in referring to the fact 

 that we did not know the colour of the living worm. But I do 

 not believe that the colour -pattern — the characteristic alternate 

 banding of many species — will fade rapidly : the worms we have 

 to deal with now have not usually been in spirit very long ; and 

 one can generally see whether fading has or has not taken place 

 to any extent. 



Again, with regard to size, I expressly wrote " within certain 

 limits" (p. 47). I meant that, for example, a worm of the size 

 of P. indica is not likely to belong to a species which in size is 

 about that of P. musica. And there is no doubt that it is some 



