34 OPINIONS AND DISCOVERIES 



advocacy of tlieir vegetable nature by Forskall and Tar- 

 gioni-Tozetti, both of them practical naturalists, and who 

 had given special attention to \^\e subject. Their observa- 

 tions went unheeded, for when a novel theory has by its 

 happily combining and connecting a number of hitherto 

 isolated facts, satisfied public opinion, the oppositions to it 

 are set aside, being reckoned among those exceptions which 

 only wait on future discovery to prove their relationship to 

 the others and their right of reception into the general 

 law. 



In 1785 Cavolini published the result of his researches 

 into the nature of sponges. They were made on the Spon- 

 gia officinalis, Lin. and on a compact fleshy species described 

 by Imperato, both of which are found plentifully in deep 

 water on the rocks of Gajoli in the bay of Naples. The fisher- 

 men here believed in the contractility of the sponge, but by 

 numerous experiments, made imder the most favourable 

 circumstances, Cavolini satisfied himself that, neither in its 

 general mass nor at the oscula, was it contractile or irritable 

 in the slightest degree, for it showed no evidence of being 

 so when torn up by hooks or when cut and lacei^ated with 

 sharp instruments ; and he had equally strong evidence for 

 saying that Linnaeus was wrong in asserting, after Ellis, 

 that the oscula or mouths were respiratory pores for suck- 

 ing in and alternately expiring the circumfluent water. Not- 

 withstanding these decisive experiments Cavolini was yet in- 

 duced to admit that a very faint degree of contractile power 

 might reside in the sponge, reminding us at the same time 

 that the appearances of it were probably caused by the pres- 

 sure of the instrument used in the experiments on the sur- 

 rounding tissue ; and he has no doubts of the sponge's ani- 



