THE PRESIDENT'S ADDRESS. 339 



distinction of animal nature, and many examples of the Alga?, 

 notably that of Volvox globator, go far beyond what is seen in 

 any of the Diatomaceae, and sometimes there is a lingering of 

 opinion here, as to which order the latter should belong. 

 Hesitation of this kind has its value, as it directs attention to 

 the subject, and, finalty, to a decision. Sponges are now 

 relegated to the animal kingdom, but it is singular that doubts 

 on this point should have belonged to modern science ; for 

 Pliny, w r ho w r rote at the beginning of the Christian era, in his 

 curious compilation, entitled " Natural History," distinctly saw 

 the true place they should occupy, though his allusion to their 

 having blood would not be accepted in the way he has expressed 

 it ; but one can understand what he means.* 



One might quote eminent names near to our own time who have 

 taken a different view, and it is remarkable, that one of such 

 large experience as the late Dr. Gray, of the British Museum, 

 should have been once on this side, and considered the spicules 

 the analogues of the hairs of plants. This comes out in a 

 passage of arms between him and Dr. Bowerbank, who could 

 not avoid giving so home a thrust as to remind him of it. 

 Even after it was generally allowed that they belonged to the 

 animal kingdom, a reservation was made for some time before 

 the fresh- water sponges were placed in the same position. 

 Observers could not have seen, as I have, the blow-fly hovering 

 over and depositing its eggs, attracted, doubtless, by the 

 offensive odour of decomposing flesh. We may thus call it 

 a scientific observer. 



My allusion to the fresh-water sponges brings me to the con- 

 sideration of the law of variation which affects all organised 

 life. It is to this law we owe the beauty in nature by which 

 we are surrounded. Science steps in to assist our observation, 

 to name the various objects, to classify them, to note the 

 divergencies one from another, thus making genera and species. 

 As regards the latter, it is the variation from a supposed 

 typical form which has become fixed, and thus well understood. 

 In the higher organisations this is not so difficult, as differentia- 

 tion is more easily seen. But, even here, the great law of varia- 

 tion is constantly making itself visible, and types may be found 



* C. Pliuii, "Nat. Hist." Lib. cxxxi., xi., "Animal esse docuimus, etiam 

 cruore inhserente." 



