I'UE president's address. 341 



could not have failed to note the changes from his type. 

 Molesey Lock became my next place of examination, where I 

 found 8. flitviatilis in large masses. A variation again is shown, 

 and half of the spicules are smooth, the other entirely spined 

 and arranged with some order, rather than intermingled one 

 with the other. At another time, being compelled by stress of 

 weather to take refuge on the floating-boat barge at Surbiton, 

 I turned it to account in a special gathering off the barge itself 

 between it and the wharfing boards, and I was interested to a 

 degree when I found that in this example nearly all the spicules 

 were entirely spined acutely. 



Now it will be seen, that the variations I have noted are so 

 far remarkable, that the smooth spicule of the type has gone 

 a complete course of alteration of a very interesting character, 

 and had I followed the example of the eminent men I have 

 quoted, I might have made two more species much more pro- 

 nounced than that they recorded. Bat it is my contention, that 

 science is better served by marking well the conditions under 

 which the examples are found, and if we append numerals 

 or letters of the alphabet it is a sufficient distinction in declar- 

 ing the variation to which this Spongilla is subject. We may 

 be a long way yet from being able to point out the laws by which 

 such is produced, but I may at least record that as far as my 

 observation goes, where the Spongilla is developed in still water 

 the skeleton spicule is smooth; but when there is agitation, and 

 perhaps according to its extent, now suspended, now renewed, 

 as in locks; and where it is constant, as was the case with the 

 example from Surbiton, the spicules were spinous. I put for- 

 ward this theory as a suggestion for farther observation, as it 

 would be interesting to discover the law by which such changes 

 as are alluded to are produced. Mr. Carter has expressed a 

 similar view.* 



There is yet another variation, of which I gave an account, the 

 example being taken from a large pond at the Manor of 

 Ditchleys, near North Weald, Essex. It was found growing 

 upon the steins of submerged plants, and thus had a very narrow 

 basis on which to develop. This would naturally affect its 



* In my paper referred to, I opposed to Mr. Carter's view the fact of 

 finding smooth spicules in a sponge from a mill-dam. confounding this with 

 the agitation of the outpour. I was therefore in error. 



