Until 1934 the life history of Syngamus trachea was usually considered to be direct though Walker in 1886 and Waite in 1920 had both tentatively suggested that earthworms play a part in the dissemination of the parasite. In that year, however, I was able to show conclusively in this laboratory that the rôle they play in transmitting the nematode is a very important one, for by means of this annelid it was possible to effect with certainty heavy infections in various birds of domestic importance. The following year it was shown also that Syngamus from starlings can easily be transmitted to chickens by earthworms: this method apparently overcomes the resistance due to a different “host strain” such as Taylor had previously encountered when he tried to infect chickens directly with material obtained from starlings. In 1938 using earthworms as vectors chickens, pheasants and partridges were easily given definite infections with various other “strains” of Syngamus. Consideration of these results made it no longer possible to ignore the importance of earthworms in the life cycle of “Gapes.”

Methods of treatment of trichinosis have been reviewed by van Someren (1938), and it was stated that no experimentally confirmed therapeutic measure had yet been found for the treatment of this disease by destruction of the nematodes in the body. In an attempt to discover a satisfactory chemotherapeutic measure, an experimental trial was made of an anthelminthic “Butolan” (Bayer), which has been shown to give very satisfactory results in cases of oxyuriasis, and in some ascariasis infections.

Numerous attempts have been made in the past to induce the eggs of Ascaris suum to hatch outside the body of the host. Extra-corporeal hatching has been observed under a variety of conditions by different workers. Kondo (1920, 1922), Asada (1921) and others record hatching in water, charcoal and sand cultures. Wharton (1915) states that hatching will occur in alkaline digestive juices, while Martin (1913) records a similar phenomenon in pancreatic fluid. Many different explanations have been offered to explain this hatching. Wharton suggested that the interaction of algae and sand might have some effect. Ohba (1923), who found that hatching would occur in 0·2% hydrochloric acid and 0·2% sodium carbonate believed that extra-corporeal hatching was limited to very old cultures of eggs. Many workers are of the opinion that some stimulus normally present in the digestive tract is necessary for hatching.

A functional buccal stylet is described in adult male and female Trichinella spiralis, and the mode of feeding of the adults is described from living specimens examined immediately on removal from the intestine. The stylet is rapidly protruded and retracted, probably for lacerating host tissue and releasing tissue fluids, and active peristaltic sucking movements of the pseudo-bulb of the oesophagus take place about once a second. The rectum shows peristaltic defaecatory movements once every two or three seconds. Intra-vitam staining with 0·01% neutral red shows an acid reaction of the stichocytes of the stichosome, which are of a granular or non-granular nature, with small tubules and alveoli in the cytoplasm.

In a previous paper (1938) it was recorded that lemon-shaped cysts of the nematode Heterodera schachtii are frequently to be found in pasture soils. In many cases the soil has not, at least for a number of years, borne a crop such as oats or mangolds likely to have been infected with this nematode. The eelworm must therefore parasitize some plant or plants commonly to be found in pastures.

In a previous paper published in 1937 Carroll & McMahon discussed the possibility of effecting control of potato root eelworm (Heterodera schachtii) by means of trap cropping with potatoes. During the past two seasons further experiments, designed with the same object in view, have been carried out. The additional information obtained from these experiments and from the experience of the past two years is presented in the present paper.

The importance of arresting the spread of the potato-strain of Heterodera schachtii, which is largely responsible for the serious disease known as “potato sickness,” has frequently been emphasised. The cysts of this nematode, as is well known, can withstand long periods of drought, and can therefore be carried about in a viable condition on any object to which small lumps of soil may become attached. In this way the eelworms may be spread, not only from one field to the next by means of farm implements, but also from one locality to another many miles away in soil adhering to seed potato tubers. Seed potatoes grown on eelworm-infected land, however free from disease in other respects, are therefore highly undesirable for planting on clean land, unless some treatment can be carried out which will kill adhering cysts. It was with the object of discovering some practical means of treating seed potatoes so that, without injury to the tubers, adhering eelworm cysts would be killed, that the experiments recorded here were undertaken.