That there are animals which inhabit the bodies of other animals as their natural locality has long been known. Many of these are so obvious as to be popularly recognized under the name of “Worms.” It is, however, only since the extensive employment of the microscope in aiding vision, that any large addition has been made to those generally known. Not only is it found that each species of animal has its peculiar parasitic animal and plant, but every species of animal appears to have a Flora and a Fauna of its own. Formerly a country was necessary to supply the materials of a Fauna or Flora, but with the microscope in hand the stomach of an insect affords abundance of peculiar species of animals and plants for such a purpose. Dr. Leidy’s work is not an account of all the species of plants found in living animals, but an account of certain new genera and species of plants discovered by himself in the stomach and intestines of a few species of insects. In an introduction, Dr. Leidy refers to the plants and animals of the human body. These are treated of at length in the works of Dujardin,* Diesing,-- and Robin.

The plants described by Dr. Leidy are as follows :—

Genus, Enterobryus, Leidy. Thallus attached, consisting of a single very long tubular cell, filled with granules and globules, producing at its free extremity one, usually two, rarely three shorter tubular cells, and growing at the other end from a relatively short, cylindroid, amorphous, coriaceous pedicle, commencing with a discoidal surface of attachment.

E. elegans is found growing from the basement-membrane of the mucous membrane of the small and large intestine of Julus marginatus, Say ; and primary part of the exterior of Ascaris infecta, Streptostomum agile, and Thelastomum attenuatum, entozoa infesting the cavities of the viscera of the same animal.

E. spiralis is found attached to the mucous membrane of the small intestine of Julus pusillus.

E. attenuatus grows from the mucous membrane of the ventriculus of the Passalus oornutus.

Dr. Leidy observes that these entophyta are found in the herbivorous Myriapoda and Coleoptera, and in no instance has he been able to detect them in species which are carnivorous.

Genus Eccrina, Leidy. Thallus attached, consisting of a very long tubular cell, filled with granules and globules, producing at its free extremity a succession of numerous globular or oblong cells, and growing at the other end from a relatively short, cylindroid, amorphous, coriaceous pedicle, commencing with a discoidal surface of attachment.

E. longa was found growing in profusion from the mucous membrane of the posterior part of the intestinal canal of Potydesmus virginiensis.

E. moniliformis was found growing upon the mucous membrane of the intestinal canal of Potydesmus granulatus.

Genus Arthromitus, Leidy. Thallus attached, by means of one or more granules, simple, cylindrical, very long, filamentous, articulate without ramuli. Articuli indistinct, with amorphous contents finally converted into solitary oval sporules.

A. cristatus grows from the mucous membrane of the ventriculus and large intestine of Julus marginatus, and also upon Enteróbryus elegans, Ascaris infecta, Streptostomum agile, and Thelastomum attenuatum ; from the mucous membrane and its appendages of the ventriculus of Passalus cornutus, and Poty-desmus virginiensis, and upon Eccrina longa.

Genus Cladophytum, Leidy. Thallus attached by means of one or more granules ; filamentous simple, with minute lateral ramuli, or branched inarticulate amorphous in structure.

C. cornutum was found in the same positions as Arthromitus. It is very minute. The filaments measured from the l-700th to the 1-lOOth of an inch in length, by the l-30000th to l-25000th of an inch in diameter.

Genus Corynocladus, Leidy. Thallus attached by means of one or more granules ; filamentous very compound ; branches thicker than the trunk, without ramuli ; inarticulate amorphous in structure.

C. radiatus was observed growing from the mucous membrane and its appendages of the ventriculus of Passulas comutus.

In addition to the above genera and species, Dr. Leidy describes some parasitic phytoid bodies, whose structure he could not well make out.

Associated with this Flora, Dr. Leidy found the following Fauna :—

In Julus marginatus were found—

Gregarina Juli marginati, Ascaris infecta, Streptostomum agile, Thelastomum attenuatum, Nyctotherus velox, Bodo Julidis, a species of Vibrio.

In Passalus cornutus were found—

Gregarina Passali cornuti, Hystrignathus rigidus.

In Blatta orientalis, the common cock-roach, were found—

A species of Vibrio, a species of Bodo, Nyctotherus ovalis, a species of Gregarina, Streptostoreum gracile, Thelastomum appendiculatum. Of these, Ascaris infecta, and the genera Hystrignathus, Streptostomum, and Thelastomum, are new.

Dr. Leidy has also a chapter on pseudo-entophyta. He is inclined to regard many of the free-floating vibrio-like, not spontaneously moving filaments, as plants. The following caution may be useful :—

“In the study of the vegetable parasites of animals, particularly those of the intestinal canals, it is necessary to be careful not to confound the tissues of certain well-known cryptogamic plants, which may serve as food, or adhere to the ordinary food of such animals, with true entophyta. Thus fragments of fungi, confervas, lichens, and the spores of these, used as food, or adhering as foreign matter to food of an ordinary kind, arc liable within the intestines to be mistaken for parasites.

“In mid-winter I found beneath an old fence-rail an individual of Acheta nigra, or large black cricket, within the proventriculus of which were large quantities of what I supposed at the time to be a free, floating entophyte, resembling in general appearance the ordinary yeast fungus Tonda, but which I now suspect to be an ergot upon which the animal had fed. The plant consisted of oblong or oval vesicular bodies, apparently thickened at the poles, and filled with a colourless liquid ; but this appearance, more probably, arose from the cells being distended with a single large, transparent, colourless, amorphous globule, which pressed a small existing amount of protoplasma to each end of the cavity. The cells were single, or in rows to eighteen in number. Frequently a single cell of comparatively large size had an attached pair of cells, or rows of cells, at one or both ends. Occasionally they are met with containing one or two small round hyaline amorphous nuclei. The isolated cellules measured from the l-2500th to the l-1666th of an inch in length, by the l-8000th to the l-6000th of an inch in breadth. The rows measured up to the l-300th of an inch in length.”

He adds that it is not improbable that an occasional new species of cryptogamic plant might be discovered in the examination of the contents of the intestine of such animals as the earth-worm, herbivorous Myriapoda herbivorous insects, Chelonians and Batrachians. Some such bodies he describes, and regards it as probable that they may produce some of the cryptogamia which appear externally on animals, as Bolrytis, &c. There can be little doubt of the importance of this field of observation, and in some of these, at present obscure organisms, may yet be discovered the sources or indications of states of disease to which the animal body is subject.

The work is illustrated with ten beautiful plates illustrating the details of the structure of the new plants and animals described by Dr. Leidy,

*

Histoire Naturelle des Helminthes. Paris, 1845.

Systems Helminthian Vindoboniæ. 1850.

Histoire Naturelle des Végétaux Parasites qui croissent sur l’Homme et sur les Animaux Vivants. Paris, 1853.