404 



NEUROPTERA 



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 Perla vesicll l ae geminates ; the 



maxima : o, egg-tubes ; ov, oviduct ; r, re- 

 ceptacuhim seminis concealing the orifice of ejaClllatory duct is divided 



into three parts by constric- 



tions. In Pteronarcys and in Perla bicaudata, according to 

 Newport and Dufour, the vasa deferentia are very long and 

 tortuous, and there 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 egg is perforated by several canals. 



FIG. 257. Egg of Perla 

 maxima. (After Imhof.) 

 c, chorion ; d, oolemn ; 

 (js, glass-like covering of 

 micropyle apparatus ; /, 

 cavity under same ; y, 

 canals penetrating 

 chorion. 



