34 BULLETIN: MUSEUM OF COMPAliATIVE ZOOLOGY. 



terminal incisive teeth, the four teeth of the left mandible interlockinfr 

 with the five of the right one. The food is pulled into the mouth by 

 the retraction of the mandibles, assisted by the upper and lower lips, 

 then meets the secretions poured into the buccal cavity by the two pairs 

 of glands, and is grasped by the claws of the terminal maxillary lobes, 

 which move laterally ; the entire maxilla may also perform lateral move- 

 ments. The maxillse are situated on either side of the tongue, and their 

 tips interlock in the space left between the glossa and paraglossae, so 

 that the retraction of the maxillae — which is slight, however, as con- 

 trasted with that of the mandibles — must pull the food along the 

 dorsal surface of the glossa, and through the space which intervenes be- 

 tween the paraglossae. In this operation, the laciniae brush along the 

 surface of the glossa, which is curved so as to conduct the food between 

 the paraglossae. On the concave dorsal surfaces of the paraglossae the 

 food meets the grinding faces of the mandibles, the upward rotary move- 

 ment of which may carry it to the projecting teeth of the paraglossae. 

 I have sometimes found particles of wood held between the teeth of the 

 paraglossae and those of the epipharynx, which is opposite. The coarse 

 ventral teeth of the mandibles crush the woody fibres preparatory to a 

 finer comminution by the denticulated molar surfaces. In the grinding 

 process, the powerful adductors play the principal part, supplemented 

 by rotary movements and possibly also by forward and backward rub- 

 bings. The downward rotary movement is much stronger than the 

 reverse, judging from the size and number of the muscles concerned in 

 the two acts. During mastication the mandibles are probably with- 

 drawn into their chitinous sockets, where the pivots encounter firm 

 resistance. The pivots are perhaps lubricated by glands already 

 described. 



The comminuted food of the pharynx is sucked into the (Desophagus. 

 This occurs by the constriction and subsequent dilatation of the fore gut. 

 Once within the oesophagus, the food may be forced back by peristaltic 

 action, resulting from the successive contraction of constricting muscles, 

 until the stomach is reached, where a valve prevents the return of the 

 food into the gullet. 



Although Collembola are classed as mandibulate insects, it is evident 

 that they are also suctorial. The Collembola are closely related to 

 Campodea, a generalized type which is regarded as the representative of 

 a primitive form from which more specialized insects have been derived. 

 As already suggested by Lubbock, we may imagine the primitive insect 

 to have possessed mouth-parts resembling tliosc I have described, ca- 



