ANATOMY. pk 
organs of the two sides are connected in two places only. The halves 
of the mentum have a cross-connection below, near the middle, and 
both vertical plates are attached to a single “‘latticed process.” There 


Lateral Process 
' 
Mouth, hook 


-----Vertical plate 
Mentum 
Cardo 
Fic. 2.—Cephalopharyngeal skeleton of third-stage larva of Drosophila 
melanogaster. 
KS 
QYV 
So 
Fia. 3.—Cephalopharyngeal skeleton of third-stage larva of 
Drosophila funebris. 

Fig. 4.—Cephalopharyngeal skeleton of third-stage larva of 
Scaptomyza adusta. 
is also an unpaired prementum, not shown in these figures, lying be- 
tween the halves of the mentum and at the level of the apex of the 
lateral process. 
Fabre believed that the corresponding apparatus in the blow-fly 
served as an organ for locomotion rather than for mastication. Ob- 
servation of living Drosophila larve has convinced me that, in this 
group at least, mastication is its primary function. Locomotion is 
usually accomplished by the help of the backward-pointing ventral 
