Trichoplax.[[116]]—This anomalous animal has only been found in aquaria, originally in the marine aquarium at Graz by Schulze. It has the appearance of a large, flattened, ciliated Amoeba (1.5-3 mm. in diameter), but is distinguished by its structure. The upper surface is composed of a flattened epithelium. The lower surface is made up of cylindrical ciliated cells, which pass imperceptibly into the branched cells, embedded in a hyaline matrix, which compose the middle layer of the body. No distinct organs, and beyond simple fission, no mode of reproduction, have been observed. One species, T. adhaerens, is known, but has never been met with in a free state.
Salinella.[[117]]—This is another aquarium-animal, found by Frenzel in the Argentine, in an artificial saline solution with which he filled some aquaria. It measures .2 mm. in length, and has a somewhat flattened, barrel-shaped appearance. A single layer of ciliated cells bounds a central cavity opening at each end. Fission, and conjugation followed by encystment, have been observed. One form, S. salve, is known from salines taken from Cordova.
NEMERTINEA
BY
LILIAN SHELDON
Staff Lecturer in Natural Science, Newnham College, Cambridge.
CHAPTER V
NEMERTINEA
INTRODUCTORY—EXTERNAL CHARACTERS—ANATOMY—CLASSIFICATION—DEVELOPMENT—HABITS—REGENERATION—BREEDING—GEOGRAPHICAL DISTRIBUTION—LAND, FRESH-WATER, AND PARASITIC FORMS—AFFINITIES
The Nemertinea form a compact group, the affinities of which have not been at present clearly determined. Several species were mentioned and described in the works of various naturalists during the latter half of the eighteenth century, though their anatomy was not understood until considerably later. The first mention of any member of the group was made by the Rev. W. Borlase in his Natural History of Cornwall, published in 1758. He gives a short description and a rough figure of Lineus marinus. From that time the increase in the knowledge of the group was very gradual. New species were from time to time described, but few of the descriptions could boast of much completeness, and many erroneous views were held until comparatively recent years. The group was very variously classified, but the general arrangement in early times seems to have been to unite it with the Planarians. Valuable contributions to the history of the development were made in 1848 and the few subsequent years by Desor,[[118]] Gegenbaur,[[119]] Krohn,[[120]] and Leuckart and Pagenstecher[[121]]; and more recently by Metschnikoff[[122]] and Salensky.[[123]]