244 NATURAL HISTORY OF OUR SHORES 



trying to detach them by hand the side of the test attached 

 to the stone usually breaks away. 



Molgula impura is a simple ascidian, of about the size, 

 shape, and texture of a gooseberry. It lives unattached 

 (unless it be to a bit of gravel), in shell gravel at extreme 

 low water. Its test is strengthened by being invested with 

 grains of sand, etc. Its specific name is very badly chosen, 

 for it lives under the most hygienic of conditions in clean, 

 shell gravel, where it mast be rolled and washed by every 

 tide. 



These are but a few of the great class of tunicates. An 

 enumeration and brief description of each of our species 

 would occupy this volume. 



The Lancelet (Amphioxus). This little animal is of fish 

 like form, and was formerly classed with the fishes. It is 

 about two and a half inches long by a quarter of an inch 

 wide, somewhat flattened laterally. It is pointed at both 

 ends (hence its name, Amphi-oxus). Its colour is a nearly 

 transparent greyish buff. 



This curious little animal the " Sheet Anchor of the 

 Evolutionist," as it was called, before it was recognised 

 that every living thing is a sheet-anchor in the same sense- 

 is not very common on our shores, or at least not generally 

 so. I have walked over sandy parts of the coast where I 

 have disturbed them at every step, then again I have been 

 many consecutive years without finding one. (In the 

 Mediterranean it is common, and fishermen employ it as 

 bait.) It has folds of skin along both the dorsal and ventral 

 sides of its posterior half, which form a fin very much as 

 in the eel, but these folds are not a true fin, as they have 

 no rays, as in fishes. For a mouth it has simply an oval 

 aperture surrounded by bristlelike, tentacular filaments. 



The water taken in by the mouth enters the pharynx, 

 which is lined by a branchial arrangement, as in the 

 ascidians. The water is not " gulped " in, as by fishes, 



