Trochetia subviridis was first noticed by Dutrochet, in 1817, from specimens obtained near Chateau-Renaud, in the Department d'Indre et Loire, where it was staled at that time to be tolerably common.[1] He has described it as resembling a Leech in appearance, horizontally flattened like one, and similarly provided with a contractile disc at the posterior extremity; but differing from it in wanting the three teeth, with which leeches puncture the skin of their prey, and in possessing, on the anterior third of the body, an annular enlargement or swelling (renflement), analogous to what is seen in the common earthworm.
The length of this annelid varies considerably, individuals having been met with which measured from two to six inches.
The colour in general is greyish green, somewhat lighter beneath, as well as on the annular enlargement, while on the back are two longitudinal and parallel brown lines, scarcely noticeable at first, but which become more perceptible on immersion in alcohol, when the whole body, with the exception of these two lines, turns to a dull leaden colour above, and a pale clay-colour beneath. The late Dr. Baird, of the British Museum, on making this experiment with son)e British specimens, found that the colour left the leeches and imparted itself to the spirit, which became of a fine green hue.
The mouth is large and bilabiate, the upper lip being somewhat larger than the under one, and according to Dutrochet—and after him Lamarck[2]—there are neither teeth nor eyes. But upon the question of the presence or absence of teeth and eyes later authorities differ, as I shall presently point out.
The excretory orifice, which is large as compared with what obtains in the true leeches, is situated on the median dorsal line, a little above the posterior disc; the genital organs are placed beneath, in the middle of the annular enlargement.
But it is in its internal anatomy especially that this animal differs from the true leeches.
The alimentary system consists—1st, of a long smooth oesophagus, disposed in longitudinal folds; 2nd, a stomach of which the lining membrane is villous and of a greyish colour; 3rd, the intestine shorter than, and as large as, the stomach, with the lining membrane of a fine yellow colour, a valve separating it from the
