22 Mr. G. Newport on the existence of Branchia in Pteronarcys. 



Neuroptcra, is retained in the perfect state. On first observing 

 these organs, in the specimen received from Mr. Barnstone, I was 

 disposed to regard them only as an accidental occurrence ; but I 

 have subsequently detected the remains of them in every dried 

 specimen I have had an opportunity of examining ; and also in the 

 pupa of the same species, in which, however, they are somewhat 

 more developed. They are of the tufted or filamentous form of 

 branchise. They consist of eight pairs of branchial sacs, from the 

 exterior of which proceed numerous elongated, setose filaments, 

 which together form a thick tuft on each sac. These branchise 

 are situated, as described by Pictet in the larva state of Nemoura 

 cinerea, Pictet, over the proper spiracular orifices or entrances to 

 the great longitudinal trachege of the body, at the inferior lateral 

 parts of the thorax and basilar segments of the abdomen. The 

 first pair of sacs is in the tegument of the neck, between the head 

 and prosternum ; the second and third pairs, each of which is 

 composed of two tufts, between the prosternum and mesoster- 

 num, behind the coxrc of the first pair of legs ; the fourth and 

 fifth between the mesostcrnum and metasternum, behind the coxse 

 of the second pair of legs ; and the sixth pair behind those of the 

 third pair of legs, at the junction of the thorax with the abdomen. 

 The seventh and eighth pairs, formed each of single tufts, are at- 

 tached more laterally, the seventh to the first, and the eighth to 

 the second basilar segments of the abdomen. These latter 

 branchi?e correspond in situation in the segments to that of some 

 apparently closed or obsolete spiracles at the sides of the succeed- 

 ing segments. The situation of the branchiae themselves is thus 

 as anomalous as their existence in the perfect insect. In most 

 instances branchipe are arranged along the sides of the abdominal 

 segments of the larva, and are often employed to assist in loco- 

 motion ; but they cannot be of use for this purpose in the larvse 

 and pupae of these Perlidce which move by means of large and 

 powerful limbs. In Pteronarcys the two posterior pairs of legs 

 of the pupa have the tibiae densely ciliated, for swimming, like 

 those of the Dyticidce, so that the delicate filamentose branchiae 

 can afford little, if any, assistance in this function. The struc- 

 ture of the filaments themselves differs also from that of the fila- 

 mentose branchiae of the Siulidce, in which these organs are said 

 to be quadri- or quinque-articulated, and are employed as organs 

 of locomotion. In Pteronarcijs they are simple unarticulated 

 filaments. Each filament is soft, delicate and gradually tapered 

 from its base to its extremity, and ends in a slightly obtuse point. 

 Internally each filament is traversed longitudinally by a tracheal 

 vessel, which becomes, like the filament itself, more and more 

 slender, and at last divides into two branches, which may be 

 traced to the extremity of the filament; but I have not l)cen able 



