A pure strain of Entamoeba histolytica has been isolated and cultivated, and an attempt has been made to study and describe its whole life-history in detail.

This strain (K. 28 c) was derived from the dysenteric dejecta of a kitten experimentally infected per os by means of typical cysts from the faeces of a monkey (Macacus sinicus). It has now been under continuous cultivation for about 20 months (220 serial subcultures), and its development in vitro has been uniform throughout.

Methods have been devised, and are here described, whereby any desired stage in the life-history of this strain—amoebae, cysts, and all intermediate stages (including encystation and excystation)—can be readily procured in vitro at will.

Detailed study has shown that the trophic amoebae multiply in cultures by simple binary fission only, as they do in their natural hosts. Their mode of division is briefly described.

Encystation also occurs in vitro just as it does in the bowel, with formation of characteristic precystic amoebae and the final production of typical quadrinucleate cysts.

Excystation has been carefully studied, and it has been found that a single quadrinucleate, amoeba escapes from each cyst through a minute perforation in its wall. An account is given of this remarkable process, which has not been described previously.

The 4-nucleate excysted (metacystic) amoeba has been found to produce a new generation of trophic forms by a complicated series of nuclear and cytoplasmic divisions, which are described in detail for the first time. The final result of this subdivision is the production of eight uninucleate amoebulae by each quadrinucleate amoeba hatched from a cyst.

These amoebulae are young trophic amoebae, and not gametes or conjugants. No sexual phenomena of any sort have been observed during the metacystic itages: and the life-history of E. histolytica, as visible in vitro, is thus wholly sexual.

A development similar to that here described in the case of Strain K. 28 c has been found to occur in many other cultivated strains of E. histolytica— including a strain isolated directly from man, and a human strain experiaentally implanted in a monkey (M. sinicus) and recovered therefrom in pure culture. There are therefore good reasons for concluding that the development were described is not abnormal, and that it is probably closely parallel to that which occurs naturally inside man.

Twelve larval trematodes, herein described as Agamodistomum la-ruei n.sp., were found by Prof. La Rue, at the autopsy of a racoon, Procyon lotor lotor (Linn.), which had been kept for several months in captivity near Douglas Lake, Cheboygan County, Michigan, during the spring and summer of 1925. The parasites were found by teasing the lungs apart in water. It was not determined whether they were in the alveoli of the lungs or in the tissue. They were apparently not encysted.

During the eighteen months spent with the League of Nations International Commission on Human Trypanosomiasis, I had a unique opportunity for studying the transmissibility of the human trypanosomes by Glossina palpalis.

During the early part of 1928, a census of the rookeries in the Oxford district was carried out by the Oxford Bird Census organised by Mr E. M. Nicholson. This work raised a number of problems, of which one of the most important was that of natural checks to the numbers of rooks. Although shooting of the young rooks is one of the greatest checks on their population, Mr Nicholson's observations showed that there must also be a mortality amongst the nestlings. Lewis (1925, 1926 b) has shown that gape-worms are common in starlings (Sturnus vulgaris), and it seemed possible to us that this parasite might also be sufficiently common in rooks to cause deaths among the young birds. The gape-worm had already been recorded from the rook by Lewis (1926 a) and Baylis (1928), so that the possibility seemed well worth investigating.