118 Wisconsin Academy of Sciences, Arts, and Letters. 
of larger particles of stone to the anterior end of the case. The 
lying deep down on either side of the mid-intestine. The testes 
are similarly situated, but are not so readily observable, par¬ 
ticularly in their later stages of development, as they are then 
closely enveloped with a layer of fat of the same color as the 
surrounding fat bodies. The sperms become quite well de¬ 
veloped in the latest larval stages, but accessory organs of re¬ 
production do not appear. 
Glands of Gilson.— In the prothorax of the larva care¬ 
ful dissection discloses a small, elongated structure, with irreg¬ 
ular, wavy outlines, lying beneath the oesophagus. (Fig. 9.) 
Its anterior tapering end passes ventrad between the connect¬ 
ives uniting the sub-oesophageal and the first thoracic ganglia, 
and may be traced to a connection with the base of a curved 
chitinous spine, which, lying between the first pair of legs, curves 
forward close to the head. A microscopic examination makes it 
clear that this is a glandular structure, with its opening at the 
tip of the spine. (Fig. 10.) The posterior end of the gland 
is free in the cavity of the body and may lie either to the right 
or to the left of the median line. This is the only representative 
in P. designatus of the Glands of Gilson, so-called from the in¬ 
vestigator who first described them. The original paper was 
not available, but M. Henseval (5) has given an interesting ac¬ 
count of the glands as studied by him in several Trichopterous 
larvae. In the possession of only one of these structures, P. 
designatus comes in the same group as Limnophilus fiavicornis, 
L. rhombicus, and Anaoolia nervosa, as opposed to Phryganea 
grandis and an undetermined Phryganid in which three glands 
of a somewhat more complex structure are found, one in each 
thoracic segment. Henseval (5) offers proof of an oily secre¬ 
tion and ascribes an excretory function to these glands. 
Under direction of Prof. Wm. S. Marshall, 
Zoological Laboratory, University of Wisconsin, 
Madison, May, 1905. 
