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.

1. The distribution of glycogen and fat in Thelastoma bulhõesi has been shown to be essentially the same as in Ascaris lumbricoides.

2. The chief storage areas of glycogen are the muscle cells and the lateral lines, with smaller amounts in the dorsal and ventral lines, the intestine and the oesophagus.

3. The chief storage areas of fat are the dorsal, ventral and lateral lines, the intestine, the oocytes, oogonia and ova.

4. Fat has been found in the lumen of the intestine of several nematodes, especially in the males of Hammerschmidtiella diesingi after 24 hr. starvation.

5. Both glycogen and fat in females of T. bulhõesi were considerably reduced, except in the gonads, after 12 days starvation.

6. Staining whole mounts with oil red O was found to be the most convenient method of determining if the food reserves were being used or not.

A growth curve of the parasitic stage of Cooperia curticei was drawn from measurements of worms collected from sheep between 2 and 22 days after infection. Exsheathed third-stage larvae did not grow during the first 48 hr. in the host. However, growth commenced between 48 and 72 hr. after infection, immediately prior to the third ecdysis. Following this ecdysis, the young fourth-stage larvae increased in length until the sixth day after infection, when growth ceased with the onset of the fourth lethargus. In most worms, this lethargus was terminated by the fourth ecdysis 8 days after infection. However, even in the oldest infections, late fourth-stage larvae were found which had been unable to enter the fifth stage. The first worms to reach the fifth stage ceased growth between 12 and 14 days after infection.

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.

A description is given of a new species of paruterinid Cestode, belonging to the subfamily Paruterinae Fuhrmann, 1907, of the family Dilepididae Fuhrmann, 1907, to which the name Lallum magniparuterina gen. et sp.nov. is given. It is parasitic in the intestine of the common teal, Nettion crecca Linn.

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. A simple apparatus for feeding all stages of Rhodnius prolixus through a rubber membrane is described.

2. Observations have been made on the behaviour of Rhodnius during feeding, and on the effect of different diets on the insect.

3. Rhodnius has been shown to feed and grow successfully on freshly drawn rat and horse blood, and on whipped ox blood. Horse serum was readily taken and showed no effect on the development of the bugs until after the third stage, when they either failed to moult or emerged deformed.

Ringer's solution, aqueous solutions of ‘Marmite’ and cow's milk provided good feeds, though caused mortality after 24 hr. Stored oxalated blood killed bugs 21 days after feeding. No feeding took place when diets of water, glycine and ascorbic acid were offered.

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.

1. The growth and development of normal and sterile (i.e. symbiont-free) Rhodnius prolixus are compared. The last three instars of sterile bugs weigh less than normal ones. Sterile insects completed the first three stages of their life-histories in less time than normal insects, and at the fourth stage, nutritional deficiencies had profound effects on their further development.

2. The sensitivity of the Rhodnius symbionts, Nocardia rhodnii, to five antibiotic substances is determined. Terramycin, aureomycin and chloramphenicol are effective inhibitors.

3. The symbiotic condition in Rhodnius and the related bug, Triatoma infestans, is discussed.