404 



NEUROPTERA 



CHAP. 



and placed very near the brain. There are three thoracic and 

 ^ six abdominal ganglia on the 



ventral chain. The nerves 

 to the wings are connected 

 with the longitudinal com- 

 missures of the ventral chain 

 by peculiar, obliquely-placed, 

 short commissures. The repro- 

 ductive glands are peculiar, 

 inasmuch as in each sex 

 the pair of principal glands 

 is connected together in the 

 middle. The testes thus form 

 an arch consisting of a large 

 number of sub-spherical or 

 pear - shaped follicles ; the 

 vasa deferentia are short in 

 Perla maxima, and there are 



Fig. 256. The pair of united ovaries of Perfe vpsiVnkp MPmbnlp^ thp 



maxima : o, egg-tubes ; ov, oviduct ; r, re- ^\^ VeSlCUiaC SCminales , tne 



ceptaculum seminis concealing the orifice of ejaculatory duct is divided 



the duct and a-n accessory gland. j. j.i - i j_ 



into three parts by constric- 

 tions. In Pteronarcys and in Perla hicaudata, according to 

 Newport and Dufour, the vasa deferentia are very long and 

 tortuous, and therj are elongate vesiculae 

 seminales. The arrangement of the ex- 

 tremely numerous egg-tubes is analogous to 

 that of the follicles of the testes, so that, as 

 Dufour says, there is but a single ovary ; 

 connected with the short, unpaired portion of 

 the oviduct, there is a large receptaculum 

 seminis, and near the terminal orifice of 

 the duct there is in P. maxima an eight- 

 lobed accessory gland. 



The eggs are produced by Perlidae in 

 enormous numbers : they are rather small, 

 but peculiar in form, and possess at one 

 extremity a micropyle apparatus, covered 

 by a glassy substance through which Imhof 

 could find no orifice. On the other hand, the chorion on another 

 part of the eg^ is perforated by several canals. 



Fig. 257. Egg of Perla 

 viaxima. (After Imhof.) 

 c, chorion ; d, oolemn ; 

 gs, glass-like covering of . 

 micropyle apparatus ; I, 

 cavity under same ; g, 

 canals penetrating 

 chorion. 



I 



