REVIEWS. 
7 
length. Its colour passes through all the shades of brown to black, and is perfectly 
hair-like in its form, except that in the male -the tail-end is bifurcated, in the female, 
trifurcated (American species). No one has yet been able to trace the animal to its 
origin! The female deposits • in the water, in which is found millions of its eggs,, 
deposited in long chords. In the course of three weeks the embryos escape from the 
eggs, of a totally different form and construction from the parents. Their body is 
only the 1-450th of an inch long, and consists of two portions ; the posterior cylin¬ 
drical, slightly dilated and rounded at the free extremity, where it is furnished with 
two short spines ; and the anterior broader, cylindrical, and annulated, having the 
mouth furnished with two circlets of retractile tentaculae and a club-shaped 
proboscis. No one has yet been able to determine what becomes of the embryo in 
its normal cyclical course. Those which I observed always died a few days after 
escaping from the egg. 
“ The grasshoppers in the meadows below the city of Philadelphia are very much 
infested with a species of Gordius , probably the same as the former, but in a 
different stage of development. More than half the grasshoppers in the locality 
mentioned contain them ; but those in drier places, as in the fields west and north 
of Philadelphia, are rarely infested. The number of Gfordii in each insect varies from 
one to five ; their length from three inches to a foot; they occupy a position in the 
visceral cavity, where they lie coiled among the viscera, and often extend from the 
end of the abdomen, forward through the thorax, even into the head; their bulk 
and weight are frequently greater than all the soft parts, including the muscles, of 
their living habitation. Nevertheless, with this relatively immense mass of 
parasites, the insects jump about almost as freely as those not infested. 
u The worms are milk white in colour, and undivided at the extremities. The 
females are distended with ova, but I have never seen them extruded. 
u When the bodies of grasshoppers, containing those entozoa, are broken and laid 
upon moist earth, the worms gradually creep out and pass below its surface. Some 
specimens which crawled out of the bodies of grasshoppers, last August, have under¬ 
gone no change, and are alive at the present time (November, 1852).. 
u In the natural condition, when the grasshoppers die, the worms creep from the 
body and enter the earth. Some of the worms, put in water, lived for about four weeks, 
and then died from the growth of Achlya prolifera. What is their cyclical 
development ?” 
The facts presented in this note serve well to show the developmental 
history of entozoa. 
After some preliminary inquiries into the nature of life in general, Dr. 
Leidy proceeds to the consideration of the topics more immediately bearing 
upon the nature and origin of entozoa, and into phytic life. Interesting, 
as these topics are, and important, as bearing upon a class of questions 
which, at the present period, closely occupy the attention of the naturalist, 
we must pass them by, merely directing our reader’s attention to their con¬ 
sideration in the pages of the present memoir, recording the result of some 
of the interesting researches of our author. 
Entozoa may and do penetrate through the living tissues; but it is entirely 
by the mechanical process of boring. 
The intestinal canal of animals is most frequented by ento-parasites, on 
account of the ease with which the germs enter with the food. 
Aquatic animals are more troubled with entozoa than those which are 
terrestrial, because the water gives a better medium of access than the air. 
Terrestrial animals are more infested with ecto-parasites, because their 
