34-! THE PRESIDENT'S ADDRESS. 



growth, but would not produce a specific change of character* 

 Nevertheless, there were certain differences in the details of its 

 skeleton which separated it from that assumed as the type. 

 The spicule was smooth, in this agreeing with the theory I have 

 propounded, and there were slight differences in the proportions 

 and character of the birotulates of the stato-blast. But I main- 

 tained again that, though an interesting variation, it was not 

 entitled to be set down as a species. How my views were received 

 elsewhere will now be seen. 



When Professor Hitchcock, of the United States, was over 

 here a few years ago T gave him a specimen of the Ditchleys 

 Spongilla for his collection, and others also distributed by or 

 through me found their way to America, and I sent a slide to 

 Mr. Carter. After some time had elapsed, I heard that Mr. B. 

 W. Thomas, an earnest worker of Chicago, had found the same 

 variety in the river Calumet, and seeing its identity with that 

 of Ditchleys, and finding that, in my description, I had declined 

 specially naming it, he proposed to call it Meyenia Calumetica. 

 Then Mr. Carter, who had received a specimen from Mr. 

 Thomas, saw that it was identical with that he had received 

 from me, turned his attention to the subject, and in an elaborate 

 article in " Ann. and Mag. of Natural History " gave it 

 the name of Meyenia angustibirotulata. which title Mr. Edward 

 Potts, in his admirable " Monograph of the Fresh-water 

 Sponges of America," has accepted. Mr. Thomas then feels 

 annoyed that he should thus be superseded, as Mr. Carter had, 

 in the first instance, declared against its being a variety. For 

 myself, who first discovered it 19 years ago, and might have 

 claimed some voice in the matter, I could not be otherwise than 

 amused at the little quarrel amongst my friends, I having 

 decided against giving the variation any separate name, my 

 views leading me in another direction. One satisfaction I have, 

 however, gained in the knowledge that the Spongilla of the 

 river Calumet is also found growing upon the stems of aquatic 

 plants, as it tends to establish, what one would naturally feel, 

 that similar conditions produce similar results. 



The more we survey the material world the more the law of 

 variation presents itself, and it ought at all times to sway our 

 judgment, when we imagine Ave have arrived at sufficient 

 differentiation from a supposed type, and seek to declare it a 

 species. When the variations are slight, as in the cases to which 



