THE SPONGE. 47 



even the irritability of the sensitive plant, the sun- 

 flower, or the daisy, that folds at eventide; it is 

 rooted to one spot, it has no definite alimentary 

 canal, and it cannot even select its food." And this 

 is true ; so closely, indeed, does the animal kingdom 

 trench on the vegetable ; so nearly, at one point, do 

 they approximate. 



It was long before opinion on this subject became 

 absolutely settled. Even Ray and Linnaeus placed 

 sponges among marine vegetables, and we are in- 

 debted for more correct knowledge to John Ellis, a 

 merchant of London, who devoted his leisure to 

 natural history. After entertaining some doubts 

 on the subject, he formed the mature opinion that 

 the sponge is an animal, through the pores and 

 canals of which the water circulates. His labours 

 were rewarded, in 1768, by the Copley medal of the 

 Royal Society ; and his belief is that of most natu- 

 ralists and physiologists at the present time : among 

 whom Dr. Grant is entitled to special mention, for 

 his minute and elaborate examination of the struc- 

 ture and habits of this remarkable creature. 



The crumb of bread sponge is well described by 

 the name it bears, not only as it appears to the eye, 

 but as it feels to the touch. Another sponge* is 

 not uncommon in clear rivulets, adhering to stones : 

 its colour varies from bright green to pale brown, 

 and changes according to the action of light. From 

 this circumstance, it has been supposed that these 



* Spongia fluviatilis. 



