143 ONYX AND DIPELTIS, 



latter fact harmonizes with the manner in which the cuticula at 

 the head expands to allow of the protrusion of the lips, which are 

 ordinarily so far withdrawn that only the tips of their papillse are 

 visible. The peculiar action of the cuticula on the head may be 

 compared to the opening and shutting of an inverted umbrella. 

 When the lips and other mouth-parts are withdrawn, the cuticula 

 is drawn together and disposes itself in longitudinal folds. When 

 the mouth parts are thrust forth, and they can be thrust forth to 

 a remarkable extent (see Figs. 4 and 5), the cuticula unfolds to 

 permit the action, and the stria? become less visible. 



I am not altogether clear about the muscles by means of which 

 the foregoing movements are accomplished. It is possible that the 

 mouth may be closed by an orbicular muscle or even by the 

 elasticity of the cuticle. Threads, doubtless muscular, pass 

 obliquely backward from the pharyngeal bulb and attach them- 

 selves to the body wall. These elements, if muscular, are of 

 course retractile in function. The pharyngeal bulb is also supplied 

 with internal threads, also contractile, which if followed in the 

 direction of the lips are found to pass obliquely outward. These 

 filaments serve to protrude the spear. The action of the various 

 organs of the head and neck during the process of feeding may, 

 therefore, be thus described. The lips are thrust forth and applied 

 to the organism whose juices are to be sucked. This operation is 

 facilitated by the papillse which act as feelers and perhaps also by 

 other mouth parts acting as clutching organs. When the lips 

 have been thus applied, they are made to adhere by suction exerted 

 in the muscular posterior portion of the oesophagus. The spear is 

 next brought into play, an operation effected by the muscles 

 inside the pharynx which act against the close adhesion of the lips 

 as a resistance. Thus the spear is made to glide forward through 

 its guide and to pierce the surface held by the lips. When the 

 surface has been pierced, the liquid food beneath it is made 

 accessible and is sucked in and swallowed by means of the large 

 muscular posterior oesophageal swelling. 



This method of using the spear is somewhat unique. In 

 Dorylaimus, with which Onyx will naturally be compared as a 



