1817.] GENUS ACTINIA. 149 



4th. In all the islands there are one or more soufrieres, 

 all of which form alum rocks, and deposite sulphur, prov- 

 ing that sulphur is one of the ingredients that support the 

 combustion, and perhaps giving strength to the supposi- 

 tion, that whatever may have been the original cause of the 

 combustion, that cause is uniform, and the same through 

 all the islands. 



5th. In the irruption of cinders, lately ejected, "there 

 was a great quantity of stones thrown out, exhibiting no 

 appearance of having ever been in a state of fusion, but 

 only roasted by a considerable heat; most of these rocks 

 have every appearance of belonging to the primitive class^ 

 by their crystalline structure, and the position of their com- 

 ponent parts. From which remarks it would appear rea- 

 sonable that the following conjectures may be hazarded. 



1st. That the islands were probably thrown up from 

 the bottom of the ocean. 



2d. That the seat of combustion is more probably in 

 a substance stratified, and that sulphur is one of the com- 

 bustible ingredients. 



3d. That the substance so stratified is most probably 

 the primitive, and that consequently the combustion is in 

 the primitive region covered by the transition, which formis 

 the islands of the eastern group. 



Observations on several species of the genus Actinia; 



illustrated by figures* By C, A. Le Sueur. Read 



November 18, 1817. 



In the course of my observations on the Mollusca, I 

 had observed that several animals, of different genera, par- 

 ticularly the Hyantmi^y were possessed of a series of small 



