A large collection of avian Ascaridia from a wide diversity of hosts and localities is reported upon. It comprised six species, A. galli, A. columbae, A. compar, A. cristata, A. hermaphrodita and A. numidae. Their morphology is examined critically with reference to previous descriptions, especially in the case of A. columbae, A. cristata, A. hermaphrodita and A. compar, and a new variety of A. columbae is described.

The taxonomic significance of spicule morphology and the tubercles on the ventral surface of the male tail in Ascaridia is discussed.

A comparative study has been made of certain species of Diphyllobothrium which are primarily parasites of birds, but which have been obtained from man and other hosts, both naturally and experimentally. As a result of this work it appears that only two valid species are known in birds, namely: Diphyllobothrium dendriticum (Nitzsch, 1824) and D. ditremum (Creplin, 1825). These species differ markedly from each other in certain morphological features and there appears to be a noticeable difference in their host-adaptation, inasmuch as D. ditremum occurs only in birds belonging to the families Phalacrocoracidae, Ardeidae, Colymbidae and Anatidae, while D. dendriticum occurs naturally in birds belonging to the Laridae and other families, and experimentally also in mammals.

Measurements of 500 eggs respectively of S. bovis, S. mattheei and S. haematobium were made. These measurements included length, maximum breadth, and breadth at a point 50 microns from the non-spiked end of the egg. Statistical analysis of the results shows that it is possible, to differentiate between the three groups of eggs.

Reasons are adduced for suggesting that the statement that S. mattheei cannot infect man is not well founded; the question is under active investigation by the author.

The genera Galactosomum, Microlistrum and Stictodora are compared, and, while the first two are undoubtedly synonymous, the last is considered to be distinct.

The adult of the type-species of Galactosomum, G. lacteum, is fully described for the first time from European cormorants, and G. phalacrocoracis is regarded as a synonym.

A new species, Galactosomum fregatae, is described from the frigate-bird Fregata magnificens rothschildi.

The characters of all the species that have been assigned to Galactosomum are briefly defined, and a provisional differential key is given.

Fifteen lots of fifty individual cysts from three separate batches were exposed to the action of potato root diffusate, the hatching allowed to continue to completion and the total larvae liberated from each cyst were counted. The data obtained were analysed both as they stood and after three different transformations for variability, as well as for independence between mean and variance. Very high variability corresponding to a coefficient of variation of 1.00 was detected, and there was, moreover, a very significant correlation between mean and variance. The most suitable transformations appeared to be either logarithmic or angular—the latter being probably the more useful. The latter, moreover, tended to increase the sensitivity of analysis. The importance of residual counts when hatching is complete is emphasized even in the absence of an angular transformation of the data.

The stem eelworm Anguillulina dipsaci (Kühn) Gerv. & v. Ben., is responsible for disease in numerous plants, amongst which are teazle, Dipsacus fullonum L., the type host and red clover, Trifolium pratense L. In both cases seed harvested from infected plants will often be infected by the stem eelworm in spite of the greatest care in dressing the seed.

Kühn (1857) in describing the parasite for the first time said:— The seeds of the diseased teazles differ from those of the healthy ones. They are not half so large nor so sharply angular. Whilst the pappus of the healthy seed is stalked that of the diseased seed is sessile and almost twice as large. The worms do not completely fill the diseased seed but occur within the atrophied ovule and also as small clumps of worms within the tissue of the abnormally thickened seed coat. The worms are found not only within the diseased seeds but in all other parts of the head including the pith where they cause not only abnormal growth but death and brown discolouration of the tissues.

The lack of a rapid and reliable method of making permanent preparations of nematodes is most strongly felt in the case of the plant-parasitic forms. The method in general use for most plant- and soil-inhabiting nematodes consists in relaxing the worms by gentle heat, fixing in 5% formalin or Ditlivsen's fixative (Thorne, 1925) and then impregnating slowly with glycerine. This procedure is quite reliable for the non-plant-parasitic forms but its results with plant-parasitic worms are very uncertain. With the latter it is necessary to transfer from fixative to very dilute glycerine, usually 1.5% glycerine in 7.5% alcohol with a trace of thymol or copper sulphate to discourage moulds. The glycerine is allowed to concentrate very slowly during at least four weeks until the worms can be transferred to pure glycerine in which they are mounted. Even then the results are often disappointing for the worms very frequently collapse.

In considering this general problem recently the authors called to mind the appearance of worms stained within plant tissues by the acid fuchsin-lactophenol method (Goodey, 1987: Franklin, 1949). This method causes no collapse or distortion of the worms and takes but a few minutes from living material to permanently stained preparations. The process has now been developed for use with free specimens of Anguillulina dipsaci and plant-parasitic species of Aphelenchoides, and is as follows:

This paper describes some hitherto unrecorded aspects of trematode development in a molluscan host.

It is shown that the rate of development of Fasciola hepatica in its host Limnaea truncatula is influenced not only by temperature but by the amount of food assimilated by the snail and by the number of rediae which are in competition within a single host.

The most rapid development of the parasite will occur in hosts which have access to ample supplies of food and in which moderate numbers of rediae become established. At laboratory temperatures, infection with a single miracidium rarely leads to the establishment of more than 40 rediae, a number which is apparently adjusted to the economy of the host, since it allows development at a maximum rate.