68 Journal Xew York Entomological Society. [^'°'- xxix, 



limb, in the so-called parapodia of the annelids (see textfigure 7) as 

 is done by Borradaile, Boas, and many of the earlier zoologists. It 

 should be borne in mind, however, that in dealing with groups so far 

 apart as the annelids and Crustacea, it is impossible to do more than 

 guess as to what parts are homologous in the structures of the two 

 groups, and the comparisons made below are more in the line of 

 suggested possibilities, than definite statements of actual homologies. 

 In such annelids as Laodice rubra (textfigure 7) the anteriormost 

 parapodium consists of a main axis "en" which bears a ventral 

 cirrus " ei" and a segmented dorsal cirrus "ex." The second para- 

 podium likewise bears a dorsal gill " cp" (dotted in the figure, since 

 it is not present in the first parapodium) attached near the base of the 

 parapodium. In comparing the parts of such a parapodium with 

 those of a typical crustacean limb (textfigure 8 — compare also Fig. 

 21, Plate VII) the position of the gills " ep" of textfigure 7 corre- 

 sponds in a general way to that of the gills or epipodites " ep " of 

 textfigure 8, while the dorsal cirrus "ex" of textfigure 7 occupies a 

 position somewhat suggestive of that of the exopodite "ex" of the 

 crustacean limb (textfigure 8). The main axis of the parapodium 

 labeled " en " in textfigure 7 resembles the main axis of the crus- 

 tacean limb {"en" of textfigure 8) in position, while the ventral 

 cirrus labeled " ei" in textfigure 7, is somewhat suggestive of the 

 endite or " gnathobase " labeled " ei " in textfigure 8. It is also quite 

 possible that the main axis of the crustacean limb labeled " en " in 

 textfigure 8, represents the main axis of the limbs " en " shown in 

 textfigures 9, 10, and 11. These in turn may correspond to the main 

 axis "en" of the parapodium shown in textfigure 7, although the 

 main axis of the parapodium shows no signs of segmentation. 



Origin of the Mandibles. 



Even such primitive worm-like forms as Peripatus have developed 

 a mandible-like appendage in the mouth region (Fig. 31) ; but some 

 investigators claim that the appendage in question in Peripatus is not 

 strictly homologous with the mandibular appendage of Crustacea, 

 insects and myriopods; and since the mouthparts of insects are merely 

 modified limbs (as was pointed out over a century ago by Savigny, 

 181 6, and has been confirmed innumerable times by embryological 



