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526 W. B. HAEDY. inserted through the mouth, injected a drop of sea water containing the one in suspension or the other in solution. Later, however, I was more fortunate, and succeeded in obtaining specimens with food in the enteric cavity. In one case the prey was a Crustacean of some considerable size, so that it produced a very obvious bulging of the animal. I did not witness the capture and ingestion of the prey, but the specimen was killed before the digestive fluid had produced any change in the tissues. Fig. 21 is taken from this specimen. It also contained the remains of a previous meal in the lower part of the enteric space. Other specimens furnished other stages, and in this way, as a result of an examination of a large number of animals, I was enabled to obtain a series representing, to a certain extent, the various stages of digestion. Myriothela is carnivorous, and captures small Crustacea. In one case the meal consisted of a half-digested egg, either derived from the gonophores of the individual in question, or from those of its neighbours. 1 Digestion is carried on at first in the lower portion of the tentacle-bearing region—that is, in that region where the gland-cells are most abundant, and results in a disintegration of the prey, brought about by the agency of the digestive fluid. The gland-cells which first discharge their contents are those in the immediate neighbourhood of the meal, but even there all the cells are not affected at once, those which are most loaded with granules probably being discharged first. Some of the gland-cells in the proximal region of the blastostyles and in the foot may be found undischarged until nearly 1 The huge yolk-laden eggs, when set free from the gonophores, are taken by tentacle-like bodies, the "claspers," which hold them while development proceeds and until the actinula larva is fully formed. In March and April, however, the claspers are not always present, and the eggs formed then when ripe are shed and sink to the bottom, where they become attached. I think that further research will show that these early eggs have a more direct development than those formed later, and pass at once to the form of the adult without the intervention of the free-swimming actinula stage. It was one of these free eggs which apparently had found lodgment in the enteric cavity.
HISTOLOGY AND DEVELOPMENT OF MYBIOTHELA f HRYGIA. 527 the close of a digestive act. The disintegration of the prey is accompanied by a great amount of solution, so that after digestion has been in process for some time the enteric cavity contains a number of fragments of the prey floating in a fluid rich in proteids, which form a deeply-staining granular precipitate after treatment with corrosive sublimate. The disintegrated fragments of the meal find their way into the foot and blastostyles, the somatic fluid probably being circulated by the active movements of the animal, which include the extension and retraction of the blastostyles, and possibly by the cilia, which appear to be borne here and there by the endoderm-cells. The process of digestion is therefore largely extra-cellular; but this is not all, intra-cellular digestion takes place to a marked, but undoubtedly a subordinate extent, and is mainly, perhaps entirely, confined to the amoeboid and mobile apical cells of the villi in the tentacular region. If these cells be examined in an animal killed towards the close of digestion they will often be found to contain the more or less imperfect capsules of thread-cells or irregular fragments of hyaline material, which recall the cuticle of a Crustacean, and probably are fragments of that structure. In fig. 17 such a nematocyst is shown embedded in a turbid mass of darkly-staining material, which occupies a vacuole in the cell protoplasm. At n is another nematocyst, now no longer lying in a vacuole, but embedded in the cell protoplasm. The digestion of the food-mass with which this nematocyst was associated having been completed, the vacuole has filled up. Other interesting points may be mentioned which point to this intra-cellular digestion. In some cases an enclosed mass may be found embedding a more or less perfect nucleus. By a careful examination of different cells we may see such nuclei in various stages of disintegration, until they are finally resolved into chromatin granules which are scattered through a pseudopodial-like lobe of protoplasm, which appears to be thrust into a vacuole as the digestion of its contents becomes complete. Carmine grains injected into the enteric cavity are eagerly
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