ORDER PARENCHYMATA. 475 
are hollowed in the thickness of the entire body. A vascular 
net-work occupies the sides ; behind the alimentary orifice is 
a double system of genital organs, and the sexual intercourse 
is reciprocal. Small black points are discoverable in the 
planariz, which are probably eyes. 
These animals are very voracious, and do not even spare 
their own species. They not only multiply in the ordinary 
way, but also very easily by division, and they sometimes 
even undergo spontaneous separation. | 
We have several of them in our fresh waters. (Planaria 
lactea, Zool., Dan., &c.) 
Our coasts also abound with them, and especially with 
those of the largest size. (Pl. awrantiaca, Nob.) 
There are some whose superficies appear to be hairy. (Pl. 
brocchit, Risso.) 
Several have two tentacula in front. (Pl. cornuta, Miill.) 
M. Dugés distinguishes from them 
PROSTOMA, 
Which have an orifice at the anterior extremity, and another 
at the posterior, and 
DEROSTOMA, 
In which the alimentary orifice is underneath, but nearer the 
anterior extremity. 
To the first of these I approximate the PH@NICURI, Rud., 
or Vertumnus Otto, which have but one orifice at the anterior 
extremity. 
But one species is known, V. thethidicola, Otto, Ac. Nat. 
Cur. xi. part ii. pl. xli. f. 2. A parasite of the Thethys 
Jimbria, of a marked appearance, and often with a forked 
tail, which is the effect of laceration. 
The third family of Parenchymatous intestina, 
