It is now becoming generally recognized that there are three different amoebae which may be present in the human bowel—the harmless Entamoeba coli(Lösch) Schaudinn and “Entamoeba” nana Wenyon and O'Connor, and the pathogenic E. histolytica Schaudinn. We have discussed these three species in an earlier paper (1917), and there noted their chief distinctive characters. In the present paper we shall describe a fourth and much less common species which we have recently encountered. It differs in some respects so conspicuously from the others that it appears to us necessary to place it not only in a new species, but even in a new genus. We propose therefore the new name Dientamoeb fragilis for our amoeba, but we can discuss the question of nomenclature most conveniently after we have described the organism itself. This, therefore, we shall now do.

Part I. After a brief statement of the present unsatisfactory position regarding the life history of Polystomella crispa, an account is given of experiments with various fixatives on P. crispa, collected near Drake's Island, Plymouth. A method is described for the cultivation of Polystomella in diatom cultures, especially with Navicula mutica var., with which a flagellate (Bodo sp.) was constantly present. The identification of individual Foraminifera, and determination of growth, were often possible by some irregularity in the shell, or by noting the attachment of one or more stalked egg cocoons of an unknown turbellarian worm. The feeding of Polystomella on diatoms seized by the pseudopodia outside the shell is described; the structures previously taken for ingested algal cells inside the shell are shown to be foraminal plugs (‘bouchons’ of le Calvez) which are discarded from time to time and thrown out of the shell along with the excretory granules (xanthosomes), mostly via the canal system.Part II. Notes are given on the microspheric form and its reproduction, through the spring and summer, by schizogony. The rearing of two broods in laboratory cultures is described, with an account of the formation of a new chamber to the shell. It is concluded that a complete life cycle consisting of one microspheric and one megalospheric phase occupies a period of about two years.Part III. Sporulation of the megalospheric form is described as seen during life; and various factors are discussed which might affect the process. The relatively small size of the reproducing Polystomella with which Lister worked is ascribed to their having lived under less favourable conditions. From a study of stained preparations, certain details are added concerning the opening up of the shell, presumably to facilitate the eventual escape of the flagellate swarm spores; also concerning the accompanying cytoplasmic and nuclear changes. Some account is given of the form and structure of the swarm spores, both alive and in permanent preparations. Experiments are described which constitute an attempt to carry the life cycle beyond the stage of sporulation. They are so far unsuccessful, with one possible exception, under all the various experimental conditions which are briefly discussed in their turn.

by these animals must be enormotus. Witlh the exception of the lhay and straw, whNbich would be useful for cows, all these tons of food could be used by man himiiself; tlhe objection that thle horses are needed as a reserve for breeding and for the arnm lhas lno force, for all these animials could be liept at grass, aid' under these conditions -would liberate many mienli for essential worlk.

Plasmodia of Labyrinthula almost invariably appear in the diatom cultures and other small marine aquaria which I have kept during the last several years for a variety of purposes in Glasgow. These aquaria are stocked with material from Millport, I. of Cumbrae, and I think it quite certain that the Labyrinthula is imported thence.This amazing creature has attracted interest ever since it was first described by Cienkowski in 1867, and good figures of it have been published by Cienkowski (1867), Duboscq (1921), and Valkanov (1929). The following note is to be regarded as a commentary on previous work and a record of my own observations rather than as an exhaustive account of the organism.