1922] Branch: Internal Anatomy of Tnchoptera 259 



nine, this arrangement leaves one less pair of nerves arising from ganglion 

 eight in L. indivisus than in P. inierrupta or H. analis. 



Upon a comparison of the three Figures, Nos. 1, 2 and 3, Plate XIV, 

 a sequence of fusion is evident. This sequence places P. inierrupta 

 as the most generalized and H. analis as the most speciaHzed and L. 

 indivisus as intermediate. Vorhies, 1905, has described the nervous 

 system of Platyphylax designatus Walker and it falls between P. 

 interrupta and L. indivisus for the ganglia of the seventh and eighth 

 segments have migrated so that the gangHon for segment seven is just 

 inside the posterior margin of segment six and the ganglion for segment 

 eight remains in segment seven, but very close to its anterior margin. 

 Betten, 1901, in his description of Molanna cinerea does not show it 

 to vary from P. designatus. Pictet, 1834, figures Phryganea striata 

 Fab. to fall between P. designatus and L. indivisus with the ganglia 

 for segments six, seven and eight in segment six, but ganglia seven 

 and eight not fused. Klapalek, 18S8, does not note any variation of 

 position, but merely gives the number of gangHa and their general 

 distribution. 



From the above it seems reasonable to think that the nervous system 

 of the order will reveal grades of consolidation of the ganglia which may 

 have a decided bearing upon classification. 



REPRODUCTIVE SYSTEM. 



The writer has done very little in this system beyond the mere 

 location of the organs, for the matter seems to have been given adequate 

 attention by Zander, 1901, Lubben, 1907, and Marshall, 1907. As 

 to the period of the appearance of the organs there is a difference of 

 opinion. Pictet, 1834, Klapalek, 1888, and Vorhies, 1905, make the 

 statement that the organs do not appear until near the period of pupa- 

 tion or at least in a very old larva; Lubben, 1907, discusses conditions 

 in a transforming larva, while Marshall, 1907, speaks of the condition 

 of the organs in the youngest larva he had, but does not give the stage. 

 In all the specimens observed by the writer, the gonads appear in 

 the early forms, showing clearly both in gross dissection and sections. 

 In P. interrupta taken in October and H analis taken in late December 

 from under the ice in streams, the gonads are distinct and developed 

 far enough so that tubules may be seen, Plate XIV, Fig. 7. This period 

 is long before there are any signs of pupation either in case or lar\^a. 



Within the species two shapes of gonads appear. In P. interrupta 

 some are elongate and flat, while others are spherical. This seems to 

 point to a sex differentiation, the elongate one probably destined to 

 become female organs and the spherical ones male organs. Plate XIV, 

 Fig. 2. In gross dissection in L. indivisus only one kind of a gonad 

 was observed, this circular and plate-like of five pairs of tubules. Plate 

 XIV, Fig. 1, at gd. In each gonad there are two outgrowths or attach- 

 ments; one from the outer side and extending to the ventral body wall 

 of the second abdominal segment and resembling a supporting thread 

 or tissue, the inner side outgrowth appears as a duct and the tubules 

 of the gonad may be seen converging toward the head of this duct. 



