The eggs of Limnophora exsurda are described. The larva is in the 3rd stage when it emerges from the egg. The absence of larval trimorphism has been described in a number of dipterous larvae and appears to be correlated with a carnivorous mode of life in the larval stage. Notes on the nomenclature of L. exsurda by Mr J. E. Collin are given.

The proteolytic activity of extracts of Entamoeba histolytica has been further investigated. Casein and gelatin, but not haemaglobin, were hydrolysed. Activity was observed in the pH range 5·8 to 8·5 with optimal activity at pH 7·5 to 7·9. Activity was optimal at 37° C. and sulphydryl groups were not required. Concomitant bacteria showed no proteolytic activity. Hyaluronidase, collagenase and lecithinase could not be detected.

An inhibitor of proteolytic enzyme was present in sera of all animals tested and in egg yolk. All culture media prepared from eggs were inhibitory, but inspissation or dilution of serum inactivated the serum inhibitor. Purified trypsin inhibitors from lima and soy bean were not active against the amoebic enzyme. Proteolytic enzymes were not secreted extracellularly in vitro.

High proteolytic activity was found in two out of five invasive, freshly isolated, strains of E. histolytica and after two series of liver passages of a single strain. The significance of these observations is discussed. It is concluded that the present evidence does not convincingly demonstrate that high proteolytic activity is required for tissue invasion by amoebae, but may accompany another factor.

1. The life cycle of Cotylurus brevis Dubois and Rausch, from the cercaria to the adult, has been investigated for the first time by using laboratory-bred primary, secondary and definitive hosts. The holometabolic metamorphosis with the formation of a tetracotyle stage in a second intermediate host has been described in detail.

2. The cercaria of C. brevis obtained from Lymnaea stagnalis in Edgbaston Pool has been found to be identical with Cercaria helvetica XXXIV Dubois from Lake Neuchâtel. The total number of flame cells in the cercaria is twenty, as opposed to the fourteen in the cercaria of Cotylurus cornutus Rudolphi (= ‘Strigea tarda’ described by Mathias (1925), Harper (1929, 1931) and Wesenberg-Lund (1934)).

3. In nature the second intermediate host of Cotylurus brevis is Lymnaea stagnalis. Under experimental conditions L. pereger and L. auricularia were also found to act as second intermediate hosts, but neither Planorbis corneus, P. carinatus nor various leeches could act as second intermediate hosts.

4. The tetracotyle stage of Cotylurus brevis is morphologically indistinguishable from the corresponding stage of other species of Cotylurus.

Shunsennia gracilis is described as a new species from a wood mouse, Apodemus speciosus peninsulae Thomas and a field mouse, A. agrarius coreae Thomas, of Mt Samak in the vicinity of Chunchon, Korea. A key to the Shunsennia is presented.

1. The morphology and life history of a new haplosporidian parasite, Nephri-diophaga xenoboli sp.nov. from the gut of a millipede, Xenobolus carnifex are described.

2. The earliest stage hatched from the spore is a free uninucleate amoebula which penetrates the gut epithelium and grows into a multinucleate plasmodium.

3. The uninucleate gametes are formed by a process of endogeneous budding in the centre of the plasmodium and the sporoblast is formed as a result of fusion of two such gametes.

4. A characteristic cyst membrane enclosing about forty to fifty sporoblasts is formed immediately after fertilization is completed which is accompanied by a disintegration of the peripheral layer of the cytoplasm of the plasmodium.

5. Each sporoblast develops into a bivalved simple spherical spore, 3·0μ in diameter.