In June 1935 we observed in the intestine of an Indian squirrel, Sciurus sp.1, a coccidium which, since it has tetrazoic tetra-sporocystid oocysts, must be placed in the genus Wenyonella recently created by Hoare (1933).2

1. Nearly a quarter of a million eggs of Sialis lutaria were collected at Cambridge in 1936. About 0·6 per cent of them were attacked by a parasite.

2. The egg-parasite of Sialis is distinct from Trichogramma evanescens, and is to be called T. semblidis (Aurivillius).

3. The male of Trichogramma semblidis occurs in two forms. Neither consists merely of imperfect or degenerate individuals of the other, for the two forms are equally large and differ constantly and fundamentally in several characters. The species, therefore, exhibits true dimorphism.

4. Rearing experiments involving isolated pure lines show that it is principally the host that determines which form of the parasite shall emerge. Males reared on Sialis are of the apterous form; those reared on three species of Lepidoptera are of the winged form.

5. The dimorphism of T. semblidis is discussed in relation to other examples of dimorphism in the Hymenoptera. It is shown to have several features of special interest.

An account is given of an investigation of the causes of error in estimating virus concentrations by the local lesion method. The irregularities were found to be due to:

(1) Variations in the response of (a) whole plants; (b) individual leaves.

(2) Variations in the volume of liquid used.

(3) Variations in the probability of the production of local lesions.

(4) Variations in the percentage of leaf hairs broken during the inoculation process.

An apparatus is described, the use of which reduces these irregularities to a minimum.

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.

Difficulties encountered in the determination of species of Contracaecum from seals led the writer to undertake a comparative morpholgical study of a considerable amount of material. This included the Ascarids from seals collected by the Scottish National Antarctic Expedition (Scotia) in 1902–4, and deposited in the Royal Scottish Museum, Edinburgh, which were obtained on loan through the courtesy of Dr A. C. Stephen. In the present paper some results of this investigation are presented, and short notes are added on other species of Ascaridae recorded from Pinnipedia.

In August, 1933, I received from Colonel A. E. Hamerton, C.M.G., D.S.O., R.A.M.C. (ret.), Pathologist to the Zoological Society of London, samples of a stool obtained from an Indian rhinoceros (Rhinoceros unicornis) on exhibition in the Society's Gardens. The animal in question was at that time suffering from severe diarrhoea and wasting, and its faeces—preserved in 5 per cent formalin—contained numerous undetermined ciliates. On examination of the material I found that two kinds of ciliates were present, one a typical Entodinium (Entodiniomorpha Ophryoscolecidae), and the other an entodiniomorphous form obviously belonging to the Cycloposthiidae, but differing from all the members of this family hitherto described.

1. The reproductive cycle of the female fly was worked out at an average temperature of 24° C. The lowest egg of the right ovary develops first, and is ripe in 7 days. Ovulation never occurs earlier than the 8th day, and frequently later; it bears some relation to fertilization, for eggs in virgin females failed to ovulate for weeks. The first larva was produced in a variable time after fertilization (because of delayed ovulation), but the succeeding larvae were produced very regularly, with an average period of 9·9 days between them.

2. Pupae produced in the laboratory usually weigh less than those collected in the field. The reason for this is nutritional, and flies must take large meals at the right stage in gestation to produce large pupae. It is impossible to ensure that this happens with all flies in the laboratory.

3. Abortions are caused in captivity by flies obtaining too little blood. They may be induced in pregnant females by allowing them to take only small meals, when either an egg or a small larva is extruded. When these flies were properly fed later, they produced normal larvae.

4. A constant temperature of 30° C. causes sterility in females. Ovaries develop abnormally, embryos fail to hatch from eggs, but young larvae (in the uteri) are not adversely affected.

5. A constant temperature below 22° C. slows down the rate of development of the eggs in the ovaries and lengthens the larval period. Experiments at this temperature are complicated by inactivity of males, which leave many females unfertilized. The length of the combined embryonic and larval periods is 17½ days.

6. Experiments performed outside in the laboratory compound suggest that the period between each larva in the field (during December in Uganda) will be about 13½ days (min. temp. 16° C.; max. temp. 27° C.).

7. Flies appear to be able to breed equally well with relative humidities of 47, 88 and 100 per cent. In the drier air care must be taken with feeding, or the flies die from desiccation.

8. A temperature of 20° C. can cause pregnant females to retain their larvae for an extra 12 hours, but not longer.

During a visit to Tanganyika, thanks to the kindness and help of the Department of Tsetse Research, I was able to investigate the reproductive cycles in Glossina morsitans and G. swynnertoni, and compare them with the cycle in G. palpalis. In the previous paper in this Journal, Mrs H. N. Mellanby gives a detailed description of her work with G. palpalis, and the following comments on the similarity of the other species is all that is required.

Parasitology, Vol. 29, No. 1, 1937, p. 43.

Hoare, C. A. and Bennett, S. C. J. Morphological and taxonomic studies on mammalian trypanosomes. III. Spontaneous occurrence of strains of Trypanosoma evansi devoid of the kinetonucleus.

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