STRUCTURE OF ONYCHOPHORAN HEAD — BUTT 45 



represent a conglomerate of characteristics of Arthropoda and An- 

 nelida but despite the apparent mixture of characteristics of both 

 animal groups, they represent harmonious animals in which individual 

 differences are present." 



Pflugfelder makes this statement after discussing the relationship 

 of the first postoral commisure to the "jaws" or, as he considers them, 

 the "mandibles." I agree that one should be careful in forming ho- 

 mologies, but the same principles apply to the mandibles themselves, 

 and in regard to these very important organs Pflugfelder is so con- 

 vinced that the onychophoran "jaws" are true mandibles, that he inter- 

 polates what I consider to be an entirely imaginary ventral organ and 

 ganglion between the mandibles and the antennae in order to provide 

 a "premandibular" segment in the Onychophora that will be homolo- 

 gous with the prcmandibular segment of the arthropods. 



My purpose in undertaking this research problem was to make a 

 thorough anatomical study of the head region and particularly the 

 "jaws" and then to review the embryonic development of the head to 

 see if a different interpretation would be justified. The form used 

 for the dissections in this study was Peripatoides novae-zealandiae 

 (Hutton). 



The head of Peripatus (fig. i A) is an undifferentiated region of 

 the body, unmarked by sutures or grooves that would give any clues 

 as to its limits or segmental areas. The antennae (Ant) are large 

 and are situated on the extreme anterior end on the dorsal side. Be- 

 neath them and slightly caudad are the inconspicuous eyes and the 

 opening into the preoral cavity (Pcav). This cavity is ringed with 

 lobes that form lips which when pressed together effectively close the 

 mouth. Deeply enclosed within the preoral cavity are the feeding 

 claws (Pel), with only their tips exposed in the preoral opening. The 

 first pair of appendages behind the mouth are the slime papillae (Sip) 

 called by some investigators the oral papillae, and behind them are the 

 first pair of legs. 



A series of parasagittal dissections will indicate the limits of the 

 preoral cavity and its relation to the real mouth opening which lies 

 within the cavity itself (fig. 2 A, B, C, D). In preparation for A, the 

 head surface was removed on the dorsal side, revealing the brain 

 (Br) and the circumoral folds (Cof). In this figure the two teeth of 

 the right feeding claw (Pel) are prominent. 



The walls of the preoral cavity are deeply folded in such a way that 

 the lobes (Dl) formed between these folds are arranged radially and 

 extend onto the outer surface of the body (figs, i A, 2 A). 



