supporting lamella

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530 W. B. HARDY. singularly hyaline and structureless even with the highest powers; they do not stain at all with picro-carmine or hsematoxylin, but take a deep tinge with aniline blue and methyl green. They are of a complex character chemically, with probably a proteid basis. That they are not wholly proteid is, I think, shown by the fact that the coloration obtained with the xanthoproteic reaction, and with acidulated ferrocyanide of potassium and ferric chloride, is never intense though it is sufficiently distinct. Neither iodine nor iodine and sulphuric acid give distinctive results. They are also not of a fatty nature, for exposure for many hours to hot turpentine fails to materially change them. These are not only the most abundant, but the most permanent nutritive spheres. The second class of bodies is markedly distinct from those just mentioned, and they occur sometimes in considerable abundance. They are perhaps most noticeable at the close of a digestive act. They measure as a rule 12 /x in diameter, and are spherical bodies, each embedded in a vacuole of a vacuolate cell, which may or may not contain at the same time the small nutritive spheres. Like the latter they are sometimes homogeneous bodies showing no internal structure, and then they stain very intensely with picro-carmine (fig. 27). But they may be also found composed half of intensely staining homogeneous material, and half of more turbid material which stains scarcely at all (fig. 28). In yet other cases the intensely staining material is reduced to a small spherical nodule or patch placed excentrically on the surface of the sphere. There can be no doubt that these are various stages in the formation or destruction of the same bodies, but I do not think that the evidence at my disposal justifies me in deciding which stage is which. As a general rule, however, the smallest of these bodies, perhaps but little larger than the firstmentioned type of nutritive sphere, are homogeneous and deeply staining, while without exception the largest forms are those with the deeply-staining material reduced to an excentrically placed bleb. These bodies resemble in some respects the yolk
HISTOLOGY AND DEVELOPMENT OF MYRIOTHELA PHRYGHA. 531 spherules of the ripe egg, and they are also found in some abundance in the young buds. I can throw no light either on their special significance or on their relation to the small nutritive spheres. I might finally add that they are rarely widely distributed throughout the endoderm, but usually occur in localised patches as though they were related to some localised and special metabolic process. They are perhaps never completely absent. Though the term nutritive sphere can, I think, be applied with justice to both the preceding bodies, its application to the third class of endodermal products would be misleading, since they are merely a specialised product of the endoderm of the tentacles. When abundant, each cell of the endoderm of a tentacle may contain one of these bodies, and then they doubtless give rise to that opacity which was noted by Allmann. They form, however, a very variable element, for while one tentacle may be fully charged with them its neighbour may contain few or none. Each of these bodies is,, when fully formed, 10 /j. in diameter, and consists of a sphere which stains intensely with picro-carmine (fig. 26), and is embraced by a cup-shaped capsule with expanded edge. That these bodies play any great part or are at all concerned in the general nutrition is extremely improbable. Under certain circumstances they are discharged from the endodermcells of the tentacles and find their way into the enteric space, and are ingested and digested by the apical cells of the adjacent villi. In what I have to say concerning the formation and fate of the nutritive spheres in the following pages, I shall refer exclusively under that title to the small nutritive spheres which are so abundant and numerous. The method of formation of these bodies has been already described, and it was seen that they develop in vacuoles formed in the protoplasm of the vacuolate cells; and I see no reason to doubt, but rather every reason for agreeing with Miss Greenwood's view, that these bodies are formed from material absorbed in the fluid form
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