74 



ESSAY ON SPONGE'SV 



getables, that it is only the peculiarity of their coH ^ 

 stituent parts (which we are enabled to discover by 

 the aid of chemical science) that separates them. 

 It is not essential to the formation and growth of 

 animal substance, that a heart, brains, or even in- 

 testines, or any viscera, should exist, no more than 

 it is, that all vegetables should possess roots. 



Many species of alcyomum appear to be desti- 

 tute of motion except in that part termed the 

 polypi ; and yet these only constitute a small pro- 

 portion of this multifarious animal ; for the basis 

 from which these animated portions issue, is equal- 

 ly formed of the same material, also endued with 

 the principle of animal life. Were it not for the 

 multifarious polypi that constitute a part of al~ 

 cyonium, the characters of distinction between' 

 that and spongia, would be more indefinite. 



Whether motion has ever been discovered or 

 not in any species of sponge, is not I conceive of 

 so much importance as some naturalists would ap- 

 pear to consider. Those who are solicitous in 

 their inquiries after the animals which they have 

 supposed to construct the vesicular fabric of 

 sponges, and have expressed their surprise, that 

 in thrs age of cultivated science, no one should 

 yet have discovered, — must have taken a very li- 

 mited view of matter possessing vitality, and have 

 grounded their hypothesis only upon supposed 

 analogy. Why should it be concluded that sponges^ 

 are only the nidi of insects or vermes ; or why 



