Organs of Invertebrate Animals. 41 



particular statement, but in the general drift of what 

 remains to be said under the present head. 



2. The false feet of the prawn, of which their are six 

 pairs, are not unlike the true thoracic feet of the 

 branchiopod crustacean. Each foot consists of a 

 flattened basal joint, on the top of which, side by side, 

 are two longish flattened leaves, with ciliated edges ; 

 and this is the case substantially in stomapod, isopod, 

 and branchiopod, as well as in decapod crustaceans 

 generally, the chief differences being in the size and shape 

 of the terminal leaves, and in the fact that in the 

 stomapods one of these has a palp and a brush-like 

 process which is obviously a rudimentary gill. In a 

 word, there is nothing peculiar in these false abdominal 

 legs, for many of them are little more than exact copies 

 of the lamelliform, fin-like, thoracic legs of the branchio- 

 pods. 



3. The organs called foot-jaws differ much among 

 themselves, and from the true and false feet already 

 noticed, but their real nature is never altogether hidden. 

 There are three pairs of them, each pair having peculiari- 

 ties of its own ; and their place is always immediately in 

 front of the true feet. In the prawn the first and second 

 pairs have parts which correspond more or less closely, 

 not only to the true feet, but also to its gill and flagellum ; 

 and the third pair is still more obviously in the same 

 case. In the crab and lobster the mutual resemblances 

 of the three pairs are more striking ; and there is less 

 difficulty in detecting the likeness to the true feet 

 immediately behind them. They are evidently these 

 latter feet but very slightly modified, and any little 

 peculiarity is as evidently owing to mere differences of 

 development in one or other of the component parts, all 

 of which are there. In the squilla mantis (a stomapod), 



