528 PHILOSOPHICAL TRANSACTIONS. [aNNO I762. 



tre, or the mouth of the animal, are spread over the whole surface of the disk. 



This polype contracting itself, changes its body into an irregular hemisphere, 

 which is so covered with the several extraneous bodies that stick to it, that it 

 is extremely difficult to know the animal in this state, and to discern it from the 

 rubbish that commonly surrounds it. 



These animals are frequently found in the pools about Mount's-Bay. It is 

 rare to meet with a single one in a place, there being most commonly 4 or 3 

 of them living so near together in the same fissure of the rock, which they 

 constantly inhabit, that their expanded calyces form a row of flowers like bodies, 

 that seem to grow upon the cliffs under water. 



The 3d species, is the Hydra corollifiora, tentaculis retractilibus frondosis.* 

 This animal, in its contracted state has more the appearance of a caterpillar than 

 of a polype. Its body is covered with a dusky white skin, in which a large 

 opening appears at the thicker extremity of the body, and at the opposite end of 

 it are 5 small denticles, that surround a cavity placed in their middle. The sur- 

 face of this cylindrical body is marked with 6 double rows of perforated knots, 

 which the animal can transform into as many legs, if occasion requires, by ex- 

 tending each tuberculum into a small transparent cylinder, whose extremity, 

 like that of the suckers of the star-fish, sticks fast to every thing which the 

 animal gets hold of, and consequently serves it for an instrument, not only 

 to fix its body with, but also to push it forward, by the help of many of these 

 suckers that are formed of the several knots of different rows. The head of 

 the polype coming out of the above-mentioned opening in the skin, is of an oval, 

 and sometimes of an hemispherical figure, somewhat like the coralla of an asa- 

 rum, but much larger in size. It is quite hollow within, and consists of a dark 

 brown, yet almost transparent membrane, which, after having found the head, 

 produces the feelers that surround the large aperture at the top of it. These feel- 

 ers are 8 or 10 in number, and of the same substance and colour with the 

 head ; they are divided into several branches, to which, as well as to the principal 

 stems, many clusters of very minute papillae adhere, which make them exactly re- 

 semble small branches of trees covered with their leaves. These leaves, or papil- 

 lae, not only contribute to the beauty of the feelers, being of a pale yellow, mixed 

 with a shining white like silver, but they also render the feelers more useful 

 to the animal, in filling up the interstices between them, through which smal- 

 ler insects else might pass, without being perceived by the animal, whose natu- 

 ral food they are. This polype seems to live at the bottom of the sea, dis- 

 tant from the land. Dr. G. met but once with it on the^shore, between Penzance 



• This animal is a species of Holothuria, and is the Holotkuria pentactes of Lianem. 



