83 
of the eg’g of Tc^n 'to maruin (= If. nano) from the rat as 65 }K Linstow 
(18^>6a). by -1-2 /i to 54 lyv -tT /a: measurements which I have made 
range from of) l)v 26 /i to 52 by 86 With the exception of Dujar- 
din's ligures these sizes fall within the limits established for Jlyrneno- 
h'pts nano from man. 
Senna (1889) noticed in feces containing- completely developed eg-g-s 
of Iljfinenolepfx najof, in six cases, numerous small rounded bodies 
(tig. 48) measuring from 5 to 10 to 30 y in diameter. The smaller 
of these were homogeneous in appearance, tinted like mother-of-pearl, 
and l)ounded bv a vcrv thin memhrane. while the larger were more 
granular and tended to become oval, with a thicker membrane, as indi- 
cated by a distinctly double contour. Senna was inclined to interpret 
these as eggs in course of development. Avhich had prematurely escaped 
from the uterus, but since he found similar bodies in two cases in 
which he could not demonstrate the presence of //. nano, he was left 
in doubt with i-egard to their nature and signiticance. 
l)E-S'KL()P,MEXT AND LIFE HISTOKY. 
The well known ami usual mode of development of tapeworms of 
the family Tivniidte, to which Jlynienolepis nano belongs, is as follows: 
The eyyx containing sic-hooli'ed embryos pass out of the body of the 
detinitive host in the feces. To develop further they must be taken 
into the alimentary canal of some other animal. If the conditions ar(‘ 
suitable in this animal the embryos, after hatching, if this has not 
already taken place, bore out of the alimentary canal, and, encysted 
somewhere in the tissues of the bod}', develop into the intermediate 
stage, cystteercus or cyaticercold . as the case may be. When this ani- 
mal, the intermediate host, is eaten by an animal which can act as a 
detinitive host, the intermediate stage continues its development and 
becomes transformed into the adidt tcorni, which produces eggs, thus 
completing the cycle. As one would expect, the normal intermediate 
host is an animal- which is the natural food of the detinitive host, or 
otherwise likely to be taken into the alimentary canal of the latter. 
Lenckart (1863, pp. 395. 397), upon theoretical grounds, assum- 
ing that an interchange of hosts occurred during the life historv of 
IlyinenoJepfS nano and noticing the great similarity in the anatomical 
characters of the worm in question, of certain tapeworms from mice 
and shrew-mice and of a cysticercoid found by Stein in the meal worm,^' 
expressed the opinion that the intermediate stage was developed in 
some insect. ^ 
Hook^^ very similar in form are found in the related tapeworms of our mice and 
shrew-mice, as well as in the cysticercoid of Stein from the meal worm. (Trans- 
lation of Leuckart, 1863, p. 395. ) 
AVe content ourselves * * * with the supposition that, as in the most nearly 
related species, the worm passes its youth as a cysticerc^oid in some insect. (Trans- 
lation of Leuckart, 1863, p. 397. ) 
19203— ^'o. 18—04 3 
