homo.ogically it represents the uterus of cestodes. The ritellogene glands are two in number and are situated laterally of the longitudinal intestinal tubes; they vary in size in different species, are generally quite elongated, and are composed of numerous branches much like a bunch of grapes in form, all of which connect with a longitudinal vitello-duct (one on each side of the body); these longitudinal ducts are in turn connected by a pair of transverse ducts which unite in the median line, immediately posterior of the shell-gland, to form a common reservoir; this in turn empties into the ootyp through the short vitello-duct mentioned above. The vitellogene glands produce yolk cells which are associated with the true ovum to form the eggs.

Excretory system.-At or near the posterior extremity, generally somewhat dorsally, is situated a small pore (porus excretorius), which leads into a median terminal resicle; this latter gives off longitudinal branches; these in turn give off secondary branches which ramify throughout the body, each small branch ending in an excretory organ. Nervous system.-A set of ganglia is found at each side of the pharynx; these ganglia are connected by a dorsal commissure and give off numerous nerves to various parts of the body. The largest nerves are the two ventral longitudinal nerves which run antero-posteriorly, and can frequently be seen in fresh specimens. Development.-See p. 30.

Cattle (Bos taurus) are alleged to be infested with fifteen kinds of flukes, only two of which, the Large American Fluke and the Common Liver Fluke, are positively known to occur in the United States. Osler has found the Conical Fluke at Montreal, where it was not uncommon; he also found the same parasite in cattle in Nova Scotia.

Sheep (Ovis aries) are infested with five known species of flukes, only one of which, the Common Liver Fluke, is known to be in the United States; the Conical Fluke, as stated above, is found in Canada. Hogs (Sus scrofa domestica) harbor three known species of flukes, only one of which, the Common Liver Fluke, is found in the United States. Willach (1893) has described a Monostomum hepaticum suis from the liver of hogs; this supposed fluke is evidently a partially developed bladder worm (Cysticercus tenuicollis) (see p. 96).

DISTOMES (Flukes of the Family Fasciolidae).

Hermaphroditic Distomes (Flukes of the Subfamily Fasciolinae).

AGAMIC, OR IMMATURE, DISTOMES (Genus Agamodistomum).

This is a purely artificial group, of biologic rather than systematic nature. One immature fluke is occasionally found encysted in the muscles of hogs.

1. The Muscle Fluke of Swine (Agamodistomum suis).

[Fig. 1.]

SYNONYMY.-Distomum musculorum suis Duncker, 1896.
BIBLIOGRAPHY.-Duncker (1896).

This small (0.5 mm. to 0.7 mm. long by 0.2 mm. broad) parasite was discovered in 1881 by G. Leunis (a trichina inspector in Saxony), and has since been found by several other trichina inspectors of Germany. As it appears never to have been binomially named, I propose to call it

Agamodistomum suis. The worm lies free or encysted in the connective tissue between the muscle fibers; it is exceedingly rare and is of no known practical importance in meat inspection, except that in a superficial and careless microscopic examination it might be mistaken for sarcosporidia, or possibly for trichinae. Nothing is known of its life history, but it is supposed to be a purely accidental parasite in swine. We are not aware of its ever having been recorded in this country.

FASCIOLES (Distomes of the Genus Fasciola).

The genus Fasciola contains the large, flounder-like parasites found especially in the liver of herbivorous animals and known under the general term "liver flukes." Of these Fascioles, or "liver flukes," we find two forms in American cattle (F. magna and F. hepatica), one form (F. hepatica) in American sheep, while a third form (F. Jacksoni1) has been found in North America, South America, and in India in the liver of elephants, and a fourth form (F. gigantica1) is described by Cobbold from the liver of the giraffe. It is quite generally admitted that these Fascioles, owing to their larger size, are more harmful than other flukes.

FIG. 1.-The Muscle Fluke (Agamodistomum suis), occasionally found in the muscle of swine. (After Leuckart, 1889, p. 155, fig. 86.)

Until a short time ago it was supposed that we had but one form of fluke in American cattle, but Hassall (1891) and Francis (1891) showed, almost simultaneously, that two distinct forms are found, one form (F. hepatica) being present in the liver, very rarely in the lungs, the other (F. magna), a much larger worm, infesting both liver and lungs.

2. The Common Liver Fluke (Fasciola hepatica) of Cattle, Sheep, Swine, etc.

[Figs. 2-22.]

For anatomical characters, compare fig. 3 with key, p. 21.

VERNACULAR NAMES.-English, Common Liver Fluke; German, Leberegel, Leberwurm, Schafegel; Dutch, Botten, Leverworm; Danish, Faareflynder; Swedish, Levermask; French, Douve hépatique, fasciole; Italian, Biscuola, distoma epatico; Spanish, Caracolillo. SYNONYMY.-Fasciola hepatica Linnaeus, 1758; Planaria latiuscula Goeze, 1782; Distoma hepaticum (Linnaeus) Abildgaard (?); Fasciola humana Gmelin, 1790; Distoma (Cladocoelium) hepaticum (Linnaeus) of Dujardin, 1845; Fasciolaria hepatica (Linnaeus) anonymous, 1845; Distomum hepaticum (Linnaeus) Diesing, 1850; Distomum (Fasciola) hepaticum Linnaeus of Leuckart, 1863; Cladocoelium hepaticum (Linnaeus) Stossich, 1892. BIBLIOGRAPHY.-For bibliography, see Hassall (1894) and Huber (1894). For more technical discussion of species, see Leuckart (1889, pp. 179-328).

FIG. 2.-The Common
Liver Fluke (Fasci

ola hepatica), natural
size (original).

GEOGRAPHICAL DISTRIBUTION.-Cosmopolitan.

HOSTS.-Man, cattle, sheep, swine, and other animals. (See pp. 137-143.)

For a discussion of these forms, see Stiles, 1894-1895.

FIG. 3.-The Common Liver Fluke (Fasciola hepatica), enlarged to show the anatomical characters: a, acetabulum; c, cirrus pouch; i, intestine; m, mouth with oral sucker; o, ovary; p, pharyngeal bulb; s, shell gland; t, profusely branched

testicles; u, uterus; va,

vagina; vg, profusely branched vitellogene gland. (After Stiles, 1894, p. 300.)

passages of the liver, and produces a large number (estimated at 37,000 to 45,000) of eggs.

(b) Eggs (figs. 4 and 5).-Each egg is composed of the following parts: (1) A true germ cell, which originates in the ovary and is destined to give rise to the future embryo; (2) a number of vitelline or yolk cells, which are formed in a specialized and independent portion (vitellogene gland) of the female glands; instead of developing into embryos, the yolk cells form a follicle-like covering for the true germ cell and play an important role in the nutrition of the latter as it undergoes further development; (3) a shell surrounding the germ cell and vitelline cells, and provided at one end with a cap or operculum. The eggs escape from the uterus of the adult through the vulva, are carried to the intestine of the host with the bile, then pass through the intestines with the contents of the latter, and

are expelled from the host with the faecal

matter. Many of them become dried and then undergo no further development, but others are naturally dropped in the water in marshes, or, being dropped on dry ground, they are washed into the water by the rain, or are carried to a more favorable position by the feet of animals pasturing or passing through the fields. After a longer or shorter period of incubation, which varies with the temperature, a ciliated embryo (miracidium) is developed. At a temperature of 20° to 26 C. the miracidium may be formed in 10 days to 3 weeks; at a temperature of 16° C. the development takes 2 to 3 months; at 38° C. it ceases entirely. Experiments have

shown that as long as these eggs remain in the dark the miracidium will not escape from the eggshell; accordingly it will not escape during the night. When exposed

FIG. 6.-Embryo of the Common Liver Fluke (Fasciola hepatica) boring into a snail. X 370. (After Thomas, 1883, p. 285, fig. 4.)

to the light, however, or when suddenly brought into contact with cold water, the organism bursts the cap from the eggshell, crawls through the opening, and becomes a

(c) Free-swimming ciliated miracidium (fig. 6).-As already stated, this organism is entirely different from its mother. It measures about 0.15 mm. long; it is somewhat broader in its anterior portion than in its posterior portion; on its anterior extremity we find a small eminence known as a boring papilla; the exterior surface of the young worm is covered with numerous cilia, which by their motion propel the animal through the water; inside the body we find in the anterior portion a simple vestigial intestine and a double ganglionic mass, provided with a peculiar pigmented double cup-shaped eye-spot; in the posterior portion of the body cavity are found a number of germ cells, which develop into individuals of the next generation.

Swimming around in the

water, the miracidium seeks
out certain snails (Limnaea
truncatula, L. oahuensis, L. ru-
bella, see p. 43), which it im-
mediately attacks (fig. 6). The
miracidium elongates its pa-
pilla and fastens itself to the

feelers, head, foot, or other exterior soft portion of the body

FIG. 8.-Sporocyst of the Common Liver

Fluke, somewhat older than that of fig. 7, in which the germinal cells are giving

rise to rediae. X 200. (After Leuckart, 1889, p. 109, fig. 67 C.)

of the snail; some of the parasites enter
the pallial (lung) cavity and attach them-
selves there. After becoming securely
fastened to the snail the miracidium dis-
cards its ciliated covering and shortens
to about half its former length (0.07 mm.
to 0.08 mm.). The parasites now bore
their way into the body of the snail and
come to rest in the liver, or near the roof
of the pallial cavity, etc., the movements
gradually cease, and we have before us the stage known as the-

FIG. 7.-Sporocyst of the Common Liver Fluke which has developed from the embryo, and contains germinal cells. X 200. (After Leuckart. 1889, p. 109, fig. 67 B.)

(d) Sporocyst (figs. 7 and 8).-The eye-spots, ganglionic swellings, and vestigial intestine become more and more indistinct and are finally lost. The sporocyst grows slowly at first, then more rapidly, and at the end of 14 days or so measures about 0.5 mm. The germ cells mentioned as existing in the posterior portion of the miracidium now develop into individuals of a third generation, known as

(e) Rediae (figs. 9 and 10).-The rediae escape from the sporocyst when the latter are from two weeks (in summer) to four weeks (in late fall) old. Upon leaving the body of the sporocyst they wander to the liver of the snail, where they grow to about 2 mm. long by 0.25 mm. broad. Each redia consists of a cephalic portion, which is extremely motile, and which is separated from the rest of the young worm by a ridge; under the latter is situated an opening, through which the next generation (cercariae) escape. The posterior portion of the