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.

1. Entamoeba histolytica Schaudinn (vel E. dysenteriae Councilman and Lafleur), the human dysentery amoeba, is a collective species. It comprises a number of distinct races, strains, or pure lines, distinguishable from one another by the size of the cysts which they produce.2. How many such distinct races exist is still undetermined; but we have demonstrated the existence of at least five.3. There is no evidence that the different races differ in their geographical distribution, or in any character save size.4. These races remain constant in character within a given host; and the dimensions of the cysts are not determined by the action of the host upon the parasite, since two different races may coexist side by side in the same host.5. Different values for the dimensions of the cysts are obtained when these are measured in different media. Taking the measurements of living cysts suspended in physiological saline solution as representing the true value, we find that the dimensions of cysts in iodine solution are approximately the same; but that cysts which have been suitably fixed, stained, and mounted in balsam, have undergone an apparent reduction of approximately 10% from the true diameter.6. The most suitable fixative for E. histolytica cysts we have found to be a modification of Schaudinn's fluid. (Saturated aqueous solution of corrosive sublimate, two parts; absolute alcohol, one part; glacial acetic acid, 4–5%.) Cysts fixed in this fluid undergo no measurable shrinkage or swelling in the process.7. The apparent loss of size observed in cysts which have been fixed, stained, and mounted in balsam, is due chiefly to the invisibility of the cyst wall in the mounting medium.8. It follows from what has been said above (5 and 6) that to obtain an approximately true value for the dimensions of the living cysts from measurements made upon those suitably fixed, stained, and mounted in balsam, these measurements should be multiplied by the factor 9. We find no evidence of the existence of a sexual dimorphism in the cysts belonging to a single race, such as has been described by Mathis and Mercier.10. Since cysts of E. histolytica may be found with all diameters from about 5μ. to about 20μ—a range overlapping or covering the dimensions of the cysts of the two common harmless intestinal amoebae of man (E. coli and E. nana) and of other cysts and cyst-like bodies occurring in human faeces—it is of considerable practical importance to recognize and distinguish the diverse races of E. histolytica which differ from one another in the dimensions of the cysts which they produce.

The paper by Apstein (1911) is the only previous work known to me which is concerned with parasites of marine pelagic Crustacea in general, chiefly Copepoda, and especially of Calanus finmarchicus. It is of the nature of a preliminary note, since his work in the neighbourhood of Kiel was suddenly interrupted in its early stages; so that, while some of his “parasites” are easily identifiable, the scanty notes on others are difficult of interpretation and have given much trouble to subsequent writers. After making observations on the parasites of Calanus in the Clyde Sea Area over a period of several years, I feel in a position to offer the following opinions on Apstein's note together with an account of very early stages in the development of some larval Platyhelminthes.

The purpose of this note is to record the occurrence of a haemogregarine parasite in the red blood corpuscles of the South American lung-fish, Lepidosiren paradoxa.

An account is given of the parasites reputed to be of protozoan nature which were observed in Calanus finmarchicus in the Clyde Sea Area, during the years 1933 to 1936. These comprise Blastodinium, Syndinium, some Gregarines, an ectoparasitic Ciliate new to science, Paradinium, Ellobiopsis, and Ichthyosporidium, besides early stages in the development of some Platyhelminth worms. A special study is made of Paradinium, which was plentiful throughout the summer months, and of the effect of the plasmodial parasites on their hosts.