The Province of Quebec provides a magnificent field for fresh-water faunistic and ecological research on account of its numerous rivers and lakes. Investigations in ecology and ecological parasitology by the authors have revealed a rich fauna in the areas described herein.

Examinations of fourteen species of fresh-water fish have produced twenty-eight species of Myxosporidia, of which twenty-five are new and three have been already described. The existence of races or strains or varieties of some of the forms is demonstrated.

Descriptions and illustrations are given of twenty-eight Myxosporidia found by the authors in fresh-water fishes of Quebec Province. The new species include: Sphaerospora notropis, Myxidium percae, Zschokkella salvelini, Myxosoma notropis, M. commersonii, M. orbitalis, M. pfrille, M. media, M. ellipticoides, M. parellipticoides, Myxobolus poecilichthidis, M. dentium, M. percae, M. rhinichthidis, M. notropis, M. catostomi, M. couesii, M. hybo-rhynchi, M. subcircularis, M. transversalis, M. grandis, Henneguya fontinalis, H. fontinalis var. notropis, H. percae, H. salmonis and H. esocis. Myxosoma catostomi Kudo, Myxobolus conspicuus Kudo and M. ovoidalis Fantham are described from Canadian fishes. Details are given of a series of races, strains or varieties of Thelohanellus notatus Mavor, of Myxobolus catostomi, of M. notropis and of Henneguya fontinalis from other than the original host fish.

The pathology of the myxosporidian infections from the many different situations in the hosts is discussed. Unusual sites of infection are the palatine teeth of Esox maskinongy with Myxobolus dentium and the iris of the eye of Couesius plumbeus with Myxobolus couesii.

In connexion with the economic importance of the Myxosporidia found in Quebec fishes, the destruction of young fish, alteration of the character of the fauna dependent on the same, human food supply, possible epizootics in hatcheries and possible cross-infection of game fishes and other fishes of economic importance are considered. The immediate danger is not great; it is the future that may be imperilled.

The paper deals with the biology, morphology and anatomy of seven species of syrphid larvae viz. Syrphus luniger Meig., S. balteatus De Greer, S. ribesii Linne, Catabomba pyrastri Linne, Sphaerophoria flavicauda Zett., Sph. scripta Linne, and Platychirus scutatus Meig.

The habitat, mode of progression, aphidophagous habits and characteristic coloration are described for each species.

It is shown that the larvae of all the above species, like larvae of other cyclorrhaphous Diptera, definitely pass through three stages separated by two moults. The mode of dehiscence of the puparium is described briefly.

Each of the species, except Catabomba pyrastri, has three generations in the breeding season which lasts from May to October. Platychirus scutatus hibernates only in the larval stage, but the other species may be found in both the larval and pupal stages during the winter.

The larvae of all the above species, except Syrphus balteatus, are commonly parasitized by ichneumonid larvae.

The morphology of the egg, the three larval stages and the puparium of S. luniger is described in detail.

The characters common to the third stage larvae of all the species dealt with are summarized and short descriptions of the third stage larvae and puparia of the individual species are given. The general appearance of the living larvae and details of the buccopharyngeal armature, spiracles and puparia of each of the species is represented in figures.

In connexion with the pupae a number of new structures are described and it is suggested that some of them are concerned with the formation of the characteristic shape of the puparium and with the dehiscence of the puparium.

Internal pupal spiracles are present in all the species dealt with, but external pupal spiracles are present only in Platychirus scutatus.

The anatomy of P. scutatus is described and figured, an account being given of all the structures except the musculature of the body wall. Study of the anatomy affords evidence as to the carnivorous mode of life of the larvae and also indicates that the larvae have evolved from aquatic forms.

The comparative morphology of the Syrphinae is discussed with respect to the relationship of the Syrphinae to other Aschiza and to the cyclorrhaphous Diptera.

Cases of myiasis by Hypoderma in a human subject in Great Britain are of sufficient rarity to warrant the recording of the following case.

A larva taken from a “small abscess on the neck of a boy aged 10”, was sent to the British Museum (Natural History) by Mr Colin Matheson of the National Museum of Wales, with a request that it be identified. The specimen was not in particularly good condition but after examination it was determined as a fully grown first stage larva of Hypoderma bovis de G. (the “second stage” larva of MacDougall (1930), “third stage” of Laake (1921), “first stage” of Knipling (1935)).

Cephalobus parasiticus is described from eleven out of sixteen young specimens of Macacus irus mordax (synonym, M. cynomolgus) caught in the vicinity of Batavia.

The species, which strikingly resembles and is easily capable of being confused with the rhabditiform free-living generation of Strongyloides, is found in the stomach and intestine of the monkeys but is apparently non-pathogenic. This nematode appears to be unable to establish itself in the rat and guineapig but is capable of being propagated indefinitely on bouillon agar at room temperature.

Uncertainty and disagreement still exist among protozoologists regarding the proper name of the trichomonad flagellate which is commonly found in the human mouth and generally called “Trichomonas buccalis”. The nomenclature of this organism undoubtedly presents several awkward problems; but I believe all of them can be solved simply and satisfactorily if we merely read aright the description recorded by its discoverer, and consequently recognize the validity of his original specific name.