. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. TRACHEAE IN THE NYMPH OF PLATHEM1S 349 trachea—then just back of the mesothoracic ganglion it receives two branches, one from the mesothoracic branch (Fig. 2, MSB) and the other from the mesothoracic trachea itself (Fig. 2, MS TH). Finally the neural trachea receives two branches pos- teriorly. The first arises from the metathoracic branch (Fig. 2, M T B) the second from the metathoracic trachea (Fig. 2, MT 777). In addition the metathoracic ganglion as previously de- scribed receives fine tubes from the tracheae whi
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. TRACHEAE IN THE NYMPH OF PLATHEM1S 349 trachea—then just back of the mesothoracic ganglion it receives two branches, one from the mesothoracic branch (Fig. 2, MSB) and the other from the mesothoracic trachea itself (Fig. 2, MS TH). Finally the neural trachea receives two branches pos- teriorly. The first arises from the metathoracic branch (Fig. 2, M T B) the second from the metathoracic trachea (Fig. 2, MT 777). In addition the metathoracic ganglion as previously de- scribed receives fine tubes from the tracheae which supply the first abdominal ganglion. From the dorsal trachea posterior to the metathoracic there arise four tubes connecting the dorsal with the lateral trachea (Fig. i, D L C). The lateral tracheae at the anterior end are not much larger than these dorsolateral connectives. Rectal brancliice. — Like many of the larval dragon flies Plathe- inis lydia takes in air from the water which passes in and out of the rectum. The rectum of the nymph is proportionately much larger than in the adult. It is supplied with a complicated apparatus for separating the air from the water. The posterior end of the ab- domen at the anus is provided with anal spines. There are three larger spines and a pair of smaller ones. Of the larger ones, two are ventral, one is dorsal while there is a single smaller spine be- tween the dorsal and each of the ventrals. Just internal to these spines are three valves each adjacent to one of the larger rectal spines. The /^-'"""^xv^0 R V dorsal valve (Fig. 3, D R V)\s the larg- est, the two ventral valves (Fig. 3, VR V) are of equal Each edge of the dorsal valve is met by the external edges of the other two, a triradiate slit being thus formed when the valves are closed. The ventral valves seem to work on the dorsal valve as a base. When the valves close water is retained in the rectum. It is forced out again by the compression of the
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
