MADREPORA. 347 



more exacl: obfervations, and an accurate figure of the 

 animal by Dr. DonatL Dr. Peyfonell has great merit in, 

 fome things ; but many of his difcoveries feem to proceed 

 more from general conclusions, taken for granted from 

 fome particular difcoveries, than from judicious and care- 

 ful experiments. In his account of Sponges, he firft 

 makes them the fabric of the Urtica marina ; in another 

 trial he makes them the fabric of little infects, that walk to 

 and fro in the labyrinth of the tubes, and which taken 

 out and placed near them, return into their holes again 1 

 but later experiments mew, that he was entirely miftaken 

 in both. See the account of Sponges in the Philofophi- 

 cal Tranfactions, Vol. $$. pag. 280. 



Dr. Donati has mofl clearly explained the nature and 

 formation of one of this genus of Madrepores by defcrib- 

 ing and delineating the animal, as we find it in Phil. 

 Tranf. vol. 47. p. 105. tab. 4. He obferves, p. 106. that 

 <c as the figure of this animal bears no refemblance to the 

 " Urtica marina, he cannot fee how one could clafs the 

 ** polypus of the Madrepora with the Urtica." Perhaps 

 it may be neceffary to obferve, that as the internal ftruc- 

 ture of the cells of many fpecies of this genus differs 

 in the appearance and difpofition of their lamella, fo we 

 may reasonably fuppofe, that the fiiape of the particular 

 animals that form them, may vary from one another. 

 But we muft leave the particular figures of thefe animals 

 to future difcoveries. 



Laftly, nothing can demonftrate more clearly the 

 great affinity there is in the growth of Corals with that 

 of fhells, than to compare the circles of increafe in 

 the fhell of the Limpet, or Patella, with thofe in the un- 

 der part of the Madrepora Fungites. In the Limpet, the 

 animal is under the fhell ; in the Coral, it is upon the 

 ihelL How abfurd, then, is it to fuppofe that Corals 



U 2 compounded 



