246 RESEARCHES IN HELMINTHOLOGY AXD PARASITOLOGY. 



communication with the intestinal canal I could not detect. Poste- 

 rior to the ventriculuS; the bod}^ is occupied with a fluid, finely 

 granular, and a coarsely granular oil-like matter. The remainder 

 of the interval of the body is filled with fluid and faintly granular 

 matter. 



Measurements. — Length, i to 2 lines ; breadth at mouth, i -600th 

 inch ; breadth at commencement of ventriculus, i -280th inch ; 

 greatest breadth about middle, i - 1 50th inch ; breadth just in advance 

 of anus, i-25oth inch. Length of caudal spine, i-25ooth inch ; from 

 base of spine to anus, i -300th inch ; breadth of ventriculus at com- 

 mencement, i-32othinch; breadth of ventriculus at middle, i-2i4th 

 inch; breadth of ventriculus at termination, i -280th inch. 



This entozoon I have seen in hundreds of the Passalus, at all 

 seasons of the year, but in none did I ever discover it in any other 

 stage of development than the one just described. 



From the frequency and great numbers in which it is found, I 

 thought it would afford an excellent opportunity to try the experi- 

 ment, if, upon introduction into another animal, it would undergo 

 any progress in its development. I accordingly obtained from the 

 forests in our neighborhood, and through my friend Baird from 

 the forests near Carlisle, over 200 individuals of Passahis Cornutiis. 

 A dozen of them I opened, and found them all infested with great 

 numbers of the entozoon just described, and I therefore naturally 

 concluded from this fact, in addition to past experience, that most 

 or probably all the other insects contained the same. Having ob- 

 tained a dozen large frogs {^Rana pipietis), after keeping them two 

 weeks until they had voided all indigesta from the alimentary canal, 

 I killed eight of them, and examined them closely for entozoa. In 

 seven I found in the lungs Distomum vahe^attim ; in all, Distonuoii 

 cygnoides in the bladder ; none in the intestines ; and in five an im- 

 perfect stage of a species of Filaria beneath the mucous coat of the 

 stomach, in the mesentery, and in the abdominal muscles 



The remaining four frogs I then fed daily upon 10 individuals of 

 Passalus conudiis each for four days in succession, so that each frog 

 in that time took 40 insects, in all 160. It is not to be presumed 

 that the frogs voluntaril}^ took this prescribed fare, for I was under 

 the necessity of cutting off the legs, elytra, and mouth organs of the 

 insects, and then forcing them into the throat of the frogs. 



In twenty-four hours after taking the first involuntary dose of 

 insect food the frogs commenced voiding the indigestible pergamen- 

 taceous segments of the skeleton of the insects per anum, which they 



