152 MORPHOLOGY OF INVERTEBRATE TYPES 



with each other by transverse anastomoses. The microscopic 

 structure of a tracheal tube is very characteristic. It consists 

 of a single layer of cells and a spiral intima or cuticle. 



Fat body. All the space between the various organs is 

 occupied by the fat body composed of very large cells. The 

 function of the fat body is not yet quite understood, but it is 

 known that it retains salts of the uric acid and that the quan- 

 tity of these salts increases with age. 



Nervous system. The nervous system of the locust be- 

 longs to the ladder or chain type. The brain or supracesopha- 

 geal mass is situated in the head above the oesophagus and is 

 composed of three neuromeres (three pairs of ganglia). The first 

 pair or the protocerebron gives off nerves to the eyes and ocelli, 

 the second or deuterocerebron to the antennae, the third or trito- 

 cerebron to the upper lip. The brain sends out two connectives 

 to the subcesophageal mass, thus forming a ring around the 

 oesophagus. The subcesophageal mass is also composed of three 

 neuromeres (three pairs of ganglia) with nerves for the postoral 

 mouth appendages, i. e., mandibles, maxillae and under lip. The 

 following two pairs of ganglia belong to the prothorax and me- 

 sothorax. The paired ganglion situated in the metathorax 

 represents the fused ganglia of this and the first abdominal 

 somite. The ganglia of the second and third abdominal somites 

 are also fused into one mass and are situated in the second ab- 

 dominal somite. The fourth, fifth and sixth somites have a 

 paired ganglion each, but the ganglion situated in the seventh 

 somite undoubtedly represents the result of a fusion of all the 

 remaining ganglia (seven to eleventh neuromeres). There is a 

 highly developed sympathetic or visceral nervous system connected 

 with the brain and supplying nerves to various organs. 



Sense organs. Like all insects the locust is a veritable 

 storehouse of sense organs. The olfactory sense is mostly re- 

 stricted to the antennae, 1 the auditory sense has for its seat the 



1 Mclndoo's observations on what he considers to be the true olfactory 

 organs in insects still need a great deal of additional proof. 



