THE THORACIC EXO-SKELETON. 179 



of a small median pit in the cervical integument. These lobes are covered 

 with fine sensory bristles, and receive a large number of nerve filaments, 

 which end in special sensory cells connected with the bristles. 



This sensory organ resembles similar, but smaller, organs situated on the 

 flexor sides of the limb articulations, and, like these, it is probably concerned 

 in indicating the movements of the parts adjacent to it, by giving rise to sensory 

 impulses originating from movements of the head and fore-limbs, by which 

 the walls of the pit in which it lies are alternately stretched and relaxed. 



The Ccmiculae are two small curved sclerites in front of the sensory lobes 

 of the sella, which form the anterior wall of the pit. '^"^'" > 3 ; o- 



The Condyles are subconical sclerosed pouches on the under and outer 

 part of the cervical integument. They exhibit three surfaces : a posterior 

 surface — which rests against the anterior surface of the thorax — an inferior 

 and an external surface. The inferior surface exhibits a curved ridge fringed 

 with hairs, with its convexity inwards. This ridge resembles a rudimentary 

 appendage ; indeed, the whole condyle, by a little modification and greater 

 development, might become a chela similar to the post-oral chelae of 

 Arachnids. The condyle is present in every insect I have examined. 



The Epicondyle (Fig. 24,7-) is a rod -shaped sclerite, which easily 

 separates from the condyle in the young imago, but which appears to be 

 inseparably united to it in the adult insect. The epicondyle articulates with 

 the cotyloid cavity of the occipital ring. A small sclerite, the first jugular 

 sclerite of Kiinckel d'Herculais lies in front of the epicondyle (Fig. 24,7^). 



Morphology of the Prothoracic Region. — The discovery of the 

 prophragma has not hitherto been recorded. It undoubtedly 

 marks the posterior limit of the dorsal portion of the pro- 

 thorax, and confirms the views of Brauer [80] and Hammond 

 [78] as to these limits. 



I regard the following sclerites as undoubtedly prothoracic 

 ■ — the prodorsum, paratremes, and epitrochleas, the sella, 

 manubrium, claviculae and pectorals. The cervical sclerites 

 also probably belong to the prothorax. I have spent much 

 fruitless labour in the endeavour to find some correspond- 

 ence between these parts and those of the meso- and meta- 

 thorax. 



My epitrochlea is certainly the trochantin of Audouin and 

 the rotula of Straus Durckheim. Both the episternum and 

 the epimeron, if they existed, should be behind the epitrochlea, 

 but they are not recognisable. The paratreme appears to me 

 to correspond with the operculum of the Hymenoptera in its 

 double relation with the prodorsum and the spiracle. Ham- 

 mond assigned it to the prothorax. I cannot accept Brauer's 



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