Ii6 



INSECTS 



CHAP. 



placed on the assumptions and calculations that are supposed to 

 prove this, and it is not supported hj Camerano's recent researches.^ 

 Some of the tendons to which the muscles are attached are 

 very elaborate structures, and are as hard as the chitinous 

 skeleton, so as to be like small bones in their nature. A very 

 elaborate tendon of this kind is connected with the prothoracic 

 trochantin in Coleoptera, and may be readily examined in Hydro- 

 philus. It has been suggested that the entothorax is tendinous in 

 its origin, but other morphologists treat it, with more reason, as 

 an elaborate fold inwards of the integument. 



Nervous System. 



Insects are provided wdth a very complex nervous system, 

 which may be treated as consisting of three divisions : (1) The 

 cephalic system ; (2) the ventral, or ganglionic chain ; (3) an 



accessory sympathetic system, or 

 systems. All these divisions 

 are intimately connected. We 

 will consider first the most ex- 

 tensive, viz. the ventral chain. 

 This consists of a series of small 

 masses of nervous matter called 

 ganglia which extend in the 

 longitudinal direction of the 

 body along the median line of 

 the lower aspect, and are con- 

 nected by longitudinal commis- 

 sures, each ganglion being joined 

 to that following it by two 

 threads of nervous matter. Each 

 of the ganglia of the ventral 

 chain really consists of two 

 ganglia placed side by side and 

 connected by commissures as 

 well as cellular matter. In 

 Fig. 64. Cephalic and ventral chain of larvae somc of the ganglia may 

 ^^l^^fm}^2''^^^tr'T'\f\ 1je contiguous, so that the com- 



imago 01 Hippooosca. (After Brandt. ) o ^ . 



missures do not exist. From 

 the ganglia motor nerves proceed to the various parts of the 

 1 Mem. Ace. Torino (2), xliii. 1893, p. 229. 



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