ESCHARIDiE. 523 



Flustra chartacea. — Ellis states : " The cells of this sea 

 mat are of an oblong square figure, swelling out a little in 

 the middle of each side. The openings of the cells are 

 defended by a helmet-like figure ; from hence the polype- 

 shaped suckers extend themselves. This sea-mat is of a 

 slender and delicate texture, like a semi-transparent paper, 

 of a very light straw-colour. It was first found on the 

 coast of Sussex, adhering to a shell. I have since met, on 

 the same coast, about Hastings, in the year 1765, with 

 several specimens whose tops are digitated, and others that 

 were very irregularly divided." 



The Flustra carbasea grow out in a leaf-like manner, 

 gradually widening to the end : they are found on shells of 

 a yellowish-brown colour ; on one of the sides the cells are 

 both large and smooth. The animals have about twenty- 

 two arms or feelers, which, says Dr. Grant, after a most 

 careful examination of these polypes, " are nearly a third 

 of the length of the body; and there appear to be about 

 fifty cilia on each side of* a tentacle, making 2200 cilia 

 ion each polype. In this species there are more than 

 eighteen cells in a square line, or 1800 in a square inch of 

 surface ; and the branches of an ordinary specimen pre- 

 sent about ten square inches of surface ; so that a common 

 specimen of the F. carbasea presents more than 18,000 

 polypes, 396,000 tentacles, and 39,600,000 cilia. 



" They are very irritable, and frequently observed to 

 contract the circular margin of their broad extremity, 

 and to stop suddenly in their course when swimming ; 

 they swim with a gentle gliding motion, often appear 

 stationary, revolving rapidly round their long axis, with 

 their broad end uppermost, and they bound straight for- 

 ward, or in circles, without any other apparent object than 

 to keep themselves afloat till they find themselves in a 

 favourable situation for fixing and assuming the perfect 

 state. The transformation of the ova, from that moving, 

 irritable, free condition of animalcules, to that of the fixed 

 and almost inert zoophytes, exhibits a new metamorphosis 

 in the animal kingdom not less remarkable than that of 

 many reptiles from their first aquatic condition, or that of 

 insects from their larva state." 



Flustra avicularis. — This is another ot the little beauties 



