ORDER INTESTINA. 461 
cut cross-wise, and consequently provided as it were with 
two lips. 
Some of them are found in the air-bladder of certain fishes, 
Ophiost. cystidicola, R. Cystidicola, Fisch. Monogr. 
ASCARIS, 
Have the body round, slender at both ends, and the mouth 
furnished with three fleshy papille, between which projects 
from time to time, a very short tube. It is one of the genera 
that is most numerous in species. They have been found in 
all sorts of animals. Those which have been dissected have 
exhibited a straight intestinal canal; and in the females, 
which form by far the greater number, an ovary with two 
branches has been observed, several times longer than the 
body, opening externally by a single oviduct, towards the 
interior fourth of the length of the animal. The males have 
but a single seminal tube, also much longer than the body, 
and which communicates with a penis sometimes double, 
which issues forth through the anus. The latter is pierced 
under the extremity of the tail. 
M. Otto, and M. Cloquet, consider as the nervous system 
of these worms, two white filaments which extend, one along 
the back, and the other along the belly; two other thicker 
threads, extending, one on the right, the other on the left, are 
regarded by some as muscular, by others, as vascular, or even 
as tracheal. 
Some have the head without lateral membranes. 
The most known species, 
Ascaris lumbricoides, L., is found without any sensible dif- 
ference in man, in the horse, the ass, the zebra, the hemionus, 
the ox, and the hog. They have been seen more than fifteen 
inches in length. Its natural colour is white. It sometimes 
multiplies to excess, and may cause mortal maladies, espe- 
