Classification of the Diplopoda. 287 



given above, thej sink into insignificance, for it will be seen 

 that the differences between Polyzonium and lulus are merelj 

 differences of degree and are due to degeneration, while the 

 characters which separate Glomeris from lulus are, at all 

 events some of them, radically different in kind. 



Although one of the particulars given by Dr. Latzel to 

 distinguish the Chilognatha from the Pselaphognatha is the 

 presence of copulatory feet in the former group, the fact that 

 the copulatory feet of the Glomeridas are not homologous 

 with the copulatory feet of the lulidse appears to be entirely 

 overlooked. Since they are not homologous their presence is 

 not a sign of relationship, but the contrary ; and it is less 

 right, because of their presence, to unite the Glomerid^e, in 

 which they occur at the end of the body, with the lulidse, in 

 which they occur in the seventh segment, as opposed to 

 Polyxenidge, in which they are entirely absent, than it would 

 be to unite the Polyxenidge with the Glomeridee as opposed to 

 the lulidse, because in the two former they are absent from 

 the seventh segment, or the Polyxenidge with the lulidae as 

 opposed to the Glomeridje, because in the two former they do 

 not occur at the end of the body. For it seems certain that 

 their independent existence in these two families, Glomeridge 

 and lulidaj, points to differentiation along diverging lines, and 

 consequent departure from some ancestral form. Further, 

 it is more than probable than this ancestral form was without 

 copulatory feet, for it does not seem likely that these organs, 

 if originally existing in the seventh segment, should have 

 entirely disappeared in the Glomeridee, or, if once acquired at 

 the end of the body, should have entirely disappeared in the 

 lulidse ; still less likely does it seem that they were present 

 in some position other than the seventh segment or the poste- 

 rior end of the body ; for if so all trace of their former exis- 

 tence has entirely and independently disappeared in the 

 Glomeridge and the lulidee, and their place has been taken by 

 organs functionally similar but morphologically different. 



Assuming, then, on these grounds that the ancestral Chilo- 

 gnath was without copulatory feet, Polyxenus certainly, in 

 this respect, more nearly resembles this ancestor than does 

 either Glomeris or lulus ^ and therefore since Glomeris and 

 lulus have been evolved along different lines from this 

 Polyxenus-YikQ ancestor, it follows that, so far as the copula- 

 tory feet are concerned, the difference between Polyxenus and 

 lulus or Polyxenus and Glomeris is less than the difference 

 between lulus and Glomeris^ and that therefore it is, at all 

 events, misleading for Dr. Latzel to advance as a character 

 by which Glomeris and lulus may be united together and 

 "^ 20* 



