History of British Entomostraca. 519 



progressive motion which the insect possesses ; and no doubt the 

 plumose nature of the filaments assists materially their power, 

 though Jurine says that, from their position in the anterior part of 

 the body, and from their motions being thus confined by the open- 

 ing of the shell, they cannot be considered as acting the part of true 

 fins ; and that their use in progressive motion is much inferior to 

 that of the anterior pair of feet. Latreille thinks these filaments 

 may also act as respiratory organs as well as the branchial plates of 

 the jaw. There is very considerable discrepancy amongst the four 

 authors I have above mentioned, as to the number of feet. Muller 

 and Ramdohr say there are only four ; the former remarking upon 

 the singularity of an insect quadruped. Straus enumerates six, 

 while Jurine says there are eight. Muller was not aware of the organs 

 which Straus calls the third pair of feet ; Ramdohr was, but consi- 

 ders them as connected with the male organs of generation, while 

 Jurine says that they are organs arising from the matrix, the use of 

 which he does not understand. In addition to the first andsecond pairs, of 

 Muller, Ramdohr, and Straus, Jurine considers the organs which 

 Muller calls " barbillons" attached to the mouth, (the palpi of the 

 mandibles of Straus) and the branchial plate of the upper jaw, as 

 two additional pairs of feet. In describing these parts of the body, 

 I shall follow Straus's nomenclature, as appearing to me the sim- 

 plest and best, and certainly the most accurate ; the figure which 

 Jurine gives of them not being at all correct. Feet, then, are six in 

 number, or three pairs. The first or anterior pair (Fig. 1. c. c- Fig. 2.) 

 are inserted immediately beneath the antennae, are the strongest of 

 all, and consist of five articulations.* The penultimate one, or 

 "'* jambe" of Straus, gives origin near to its base to several pretty 

 long filaments, varying in number and length in different species ; 

 and like those of the antennae, in the larger species, are seen to be 

 beautifully plumose, a fact not taken notice of by any author, and 

 the last articulation, the tarsus of Straus, is terminated by three pretty 

 strong hooks. This pair of feet therefore, by this organization, is 

 fitted for both swimming and walking ; the long plumose filaments 

 of the fore leg answering the same purpose, and being applied to 

 the same use as those of the antennae, causing these feet when put 

 in motion to act also as fins, while the hooks at the termination of 

 the tarsus enable it to seize hold of the plants, &c amongst which 

 they live, and thus walk from place to place. These feet are con- 

 sidered by Jurine as more deserving the name of fins than the an- 



* Jurine says eight. 



