234 EVENINGS AT THE MICROSCOPE. 



side, where the passage, which I have called the throat, 

 but which is more correctly designated the buccal funnel, 

 enters. Within this muscular bulb are placed two bent 

 organs like hammers, called mallei, and a third central 

 table, called the incus. The mallei approach each other 

 dorsally, while the incus is placed towards the ventral 

 side, its stem pointing obliquely away from the centre. 



Each malleus consists of two portions, united by a free 

 but powerful hinge-joint. The lower joint (manubrium) 

 is shaped somewhat like a shoulder-blade ; and the upper 

 joint (uncus)* is set-on at nearly a right angle to it, but 

 is capable of considerable change of direction by means 

 of its hinge. It consists of five or six finger-like teeth, 

 connected by a thin web of membrane. 



The incus also consists of several distinct pieces. The 

 principal are two stout rami, resting on what appears, 

 when you look at the back or belly of the animal, to be a 

 slender foot-stalk (fulcrum). But when you get a lateral 

 view, the foot-stalk is seen to be only the edge of a thin 

 plate, to the upper edge of which are jointed the rami, in 

 such a manner that they can open and close, like the 

 blades of a pair of shears. Each ramus is a thick, three- 

 sided piece, with the upper side hollow, and the inner 

 flat, and in contact with that of its fellow, in a state of 

 repose. The uncus of each malleus falls into the concavity 

 of its corresponding ramus, and is fastened to it by a stout 

 triangular muscle, which allows some freedom of motion. 

 Many muscles are inserted into diflerent parts of these 

 organs, and into the walls of the inastax, which impart 

 various and complex motions to all the parts. Thus, as 

 we have seen, they are adapted to the various functions 

 of mouth-organs, those of grasping, holding, bruising, 

 and chewing food. 



The mallei correspond with the mandibles of Insects ; 



* The uncus of the malleus must not be confounded with the incus. 



