OF THE ANNULOSA. 385 



contains the eyes, together with these cheliform or un- 

 guiform antenna, and which is generally distinguished 

 from the true thorax by an angular impression, the point 

 of which faces the abdomen. There is, it is true, only one 

 method of setting this matter completely at rest, which is, 

 to ascertain whether it be really with nerves answering to 

 the antennal nerves of Crustacea that those organs, com- 

 monly called the mandibles of the Arachnida, are sup- 

 plied : but in the mean time I confess that I am much 

 inclined to adopt M. Latreille's theory, because it recon- 

 ciles many circumstances which had hitherto appeared to 

 me anomalous. To give only one example : M. Savigny 

 considei'ed that the Pycnogonida connected the Arachnida 

 with Cyamus, but thought it evident that Nymphon has 

 lost not only the compound eyes and masticatory organs 

 of Cyamus, but also the antennas. He thus makes the two 

 pairs of organs, which proceed from the head of Nymphon 

 grossipes, to be the first and second pairs of true feet in Am- 

 phipod Crustacea; or, in other words, he accounts the first 

 and second pairs of feet in a Squilla, — that is, according to 

 his theory, the second and third pairs of feet in an Insect, — 

 to be nothing else analogically than the mandibles and 

 maxillae of a Spider! There is little enough of rule in this, it 

 may be said ; but there will appear still less, when we find 

 that in other Pycnogonida the pair of feet which is most apt 

 to disappear is not, as might have been expected, the first, 

 but the second. Hence, proceeding on this theory, we find 

 the principal appendages of the body of a Crab to be dis- 

 posed in a male Phoxicholus, as follows : 



1. Antenna, mandibles and maxilla, none. 



2. Second maxilla and first pair of maxillary feet, a 

 •vestige. 



2 C 



