Organs of Invertebrate Animals. 37 



as in the decapod, turns back completely, and closes 

 upon the body of the tarsus itself, while the remaining 

 three pairs have fewer joints, usually not more than three 

 or four, and are almost as rudimentary as the fin-feet of 

 the branchiopods. In point of fact, the two first pairs 

 of " true feet " in the stomapods serve to connect the 

 forceps-feet with the ordinary claw-feet of the decapods, 

 while the three hindermost pairs supply a similar bond 

 of connection between the ordinary six-jointed foot of 

 the higher crustacear and the simple fin-foot of the 

 branchiopod. 



The number of the organs which may be justly 

 regarded as " feet " in the Crustacea is by no means 

 constant. Only a few are decapods, and very many are 

 multipeds if not myriapods. And so it need not be 

 matter of wonder that the number of feet should vary 

 as it does do in annulata and insecta and arachnida 

 and cirripedia : indeed, the only inference to be drawn 

 from this inconstancy as to number is that the foot is 

 not so special and singular an organ as it seemed to be 

 at first. And this is all that need be said now except this 

 that there are transitional forms in abundance which 

 make it easy to pass without break from the feet of 

 Crustacea to the legs of other invertebrate creatures. 



And even in some points wherein at first there might 

 seem to be some peculiarity there is in reality nothing 

 of the kind. 



The simple legs of many of the branchiopods and 

 isopods, articulated only at their bases, conduct natu- 

 rally to the legs of many of the annulata : and in 

 some of these creatures, as in the Aphrodite, the leg 

 is evidently a sketch of the more complex true leg of 

 the prawn and other decapod. Here, each one of the 

 many feet is made up of a wide, soft, irritable, basal 



