PECOLIAE SENSE ORGAN IN SCUTIGBBA OOLEOPTRATA. 195 



into tlie chitinous lining of the pouch and indeed projects for 

 a short distance on the inner side of the latter. The outer end 

 is prolonged into a long fine hair. 



General Features of the Internal Anatomy. 



The hypodermic layer of cells or matrix lying beneath th,e 

 exoskeleton accompanies the chitin round the lateral recesses, 

 and at the edge of the folds which form the lateral lips of the 

 two pouches becomes continuous with a thick layer of sensory 

 epithelium which lines the greater part of the two pouches 

 (fig. 2, s. e.). On reaching the dorsal lips of the pouches, which 

 lips bound laterally the median recess, the epithelium loses its 

 sensory character and again becomes simple hypodermis. On 

 the dorsal part of the median recess the epithelium again 

 becomes sensory in character. The nerve supply is furnished 

 by two short thick nerves (fig. 2, N.) which arise from the fronjb 

 portion of the subcesophageal ganglion. The two nerves enter 

 the sensory epithelium, one to each pouch, near the posterior 

 part of the organ, and there breaks up into a number of fibres 

 which become lost in the epithelium. The form of the organ 

 as indicated by the division into two pouches (fig. 2, p.) and 

 the double nerve supply seem to me to show conclusively that 

 it is double, and that each of the two pouches with its other 

 parts is to be regarded as constituting a separate sense organ. 



Histology. 



The histology of the cellular tissues demands a more detailed 

 account. The cells forming the matrix from which the 

 exoskeleton is renewed after each moult are large, rather 

 columnar in their character, and have a well-defined nucleus* 

 They are closely applied to the chitin and accompany it up to 

 the end of the lateral recesses (refer to fig. 3, hy.) where the 

 folds forming the ventral lips of the pouches begin. Here the 

 chitin is thrown into folds somewhat like, those which charac- 

 terise the surface of the pouches. The hypodermic cells here 

 lose their regularity of outline and follow the chitin into the 



