340 thk president's address. 



changing or passing into decay. When we descend in the scale 

 of living things, animal or vegetable, our difficulties are con- 

 stant, and it is extremely doubtful, whether in many cases 

 what we make into species is but variation. That this was 

 formerly done, to a greater extent than at present, we all know, 

 but the tendency still exists, and the multiplication of names to 

 overloaded vocabularies is a serious evil. In all cases, it is most 

 important to take note of the conditions under which an 

 organism is found ; and we may then see the value of slight 

 changes from what we call the type form, but it does not follow 

 that these changes make species, but, on the contrary, are mere 

 varieties, consequent on the special conditions in which they are 

 found. 



Many years ago, I had the pleasure of communicating to you 

 a paper " On Variation in Spongilla fluwatilis." My study 

 of this was chiefly made in the Thames. Referring to the 

 Spongiada? of Dr. Bowerbank, I found that his type form was 

 from the West Country Timber Dock at Rotherhithe, of which 

 he describes the skeleton spicule as acerate, viz., sharp at both 

 ends, and he represents it as quite smooth. Now Mr. Edward 

 Parfitt, of Exeter, an ardent naturalist, discovered a specimen at 

 the Salmon Pool of the River Exe, and he detected some 

 differences between it and the type form ; and this was chiefly in 

 having one half, or nearly so, of the skeleton spicules incipiently 

 spinous, though these were less in number. Dr. Bowerbank 

 made it into a distinct species, calling it Spongilla Parfitti. A 

 portion was sent to that eminent observer in this department of 

 natural history, Mr. H. J. Carter, F.R.S., who described it in 

 the " Ann. and Mag. of Natural History " for April, 1868, as a 

 variety of Spongilla Meyeni, calling it S. Meyeni, var. Parfitti. 

 It must here be noted that the term " Meyeni " was given by 

 Mr. Carter, and it has been generally adopted. Dr. Bower- 

 bank at once criticised Mr. Carter, saying " How this British 

 Spongilla can be a variety of a species that does not exist in 

 England, is past my comprehension." 



But, in my own opinion, both were sinning in making too 

 much of a trifling variation which also I found in the Thames 

 at Teddington Lock, and variations of a much more positive 

 character in the same river ; and it seems improbable that Dr. 

 Bowerbank knew much of the Spongilla of the Thames, or he 



