446 Mr. Newport on the Anatomy and 



duct {z) formed by the union of the deferential ducts of the two sides and of 

 the seminal vesicles. At the point of union of the analogues of these parts in 

 the female the passage is dilated into a large csecal cavity, from the closed 

 end of which, on each side, proceed two diminutive caeca, the undeveloped 

 representatives of the vesiculce seminales {x) of the male. The dilated pouch- 

 like cavity in the female, the so-called spermatheca, which receives and re- 

 tains the influence of the male at the union of the sexes, is thus an enlarged 

 uteroid expansion of a portion of the common oviduct which is formed by the 

 union of the terminations of the deferential and seminal tubes of the male. 

 This is the general anatomy of these organs, both in Pteronarcys and Perla ; 

 and to which that of all other Hexapods, subject to variations in the relative 

 development of particular portions of these structures, is conformable. 



From this comparative examination of structure in Pteronarcys it may be 

 asked, what are the proper affinities of the insects of this genus ? and whether, 

 with the other Perlidce, they occupy a proper position in the arrangement of 

 systematists ? The great similarity of the digestive organs of Perla to those 

 of the Blattidce, and the remarkable existence of certain talc-like structures 

 on the head in insects of this family external to the ocelli (fig. 10), resem- 

 bling others which are known to exist at the base of the antennae in the 

 Blattidce, suggest the conclusion that if the Megaloptera, including Perla and 

 Pteronarcys, are not joined to the Orthoptera, they ought at least to follow 

 that Order, at the head of the Neuroptera, and to be succeeded by the Libel- 

 lulce, AgrionidcB and Ephemeridce, as the most natural arrangement, and as 

 most conformable to their anatomy. 



