126 THE APODID^ part i 



served. The mandibles and first maxillae have lost 

 their dorsal parapodia almost entirely, and with them 

 all traces of setiparous glands. The antennae, how- 

 ever, are in this respect especially interesting. We 

 have homologised them with the sensory cirri of the 

 vanished or rudimentary dorsal parapodia of the first 

 two segments. The acicular glands of both, however, 

 have apparently been preserved in the Crustacea. 



The Aciailar gland of tJie fit'st segment. — There is 

 a pair of glands (salivary ?) opening near the entrance 

 of the oesophagus (Fig. 29, p. 114). We think 

 that these belong almost certainly to the first 

 antennae ; ^ they open together in a small transverse 



^ We were at first inclined to think that these "salivary " glands v/ere 

 the acicular glands of the parapodia of the second antennae, there being 

 no antennal glands in Apus. Their opening in the mouth could then 

 be explained as follows : — When the Annelid first took to browsing, its 

 ventral parapodia near the mouth would not as yet have developed 

 teeth. The acicula of the antennal parapodia might then have been 

 used as piercers and killers of prey. They would thus be turned inwards 

 towards the opening of the mouth, where their glands might persist as 

 salivary glands after the development of the ventral parapodia of the 

 third and fourth segments into jaws and maxill?s had rendered the 

 acicula useless as teeth. It seemed to us more likely that the acicula 

 of the parapodia of the second segment would be so used, than that the 

 acicula of the vanished parapodia of the first segment should redevelop 

 for that purpose. We have to choose then between the following : 



(i) These salivary glands are the aciciilar glands of the parapodia of 

 the second antennae, the acicula themselves having once functioned as 

 teeth ; this homologises them with the typical antennal glands of the 

 Crustacea. 



(2) They are the acicular glands of the vanished parapodia of the first 

 antenncc which had redeveloped their acicula as teeth. 



(3) They are the acicular glands of the vanished parapodia of the first 

 antenna; which, as glands, need never have disappeared. While we 

 think the oral position of the opening of the glands is better explained 



