Owing to the comparative rarity of Paramphistomes in Britain the difficulties of attempting to work out the life cycle are very great. Upto the present the problem has been approached from two angles; firstly, where an infected animal has been found at the abattoir, and finally traced back to its farm of origin, extensive collection of snails has been carried out at the assumed site of infestation ; secondly, where it has been possible to collect large numbers of adult worms from slaughtered animals, these have been picked out of the rumen and placed in dishes containing boiled tap water for several hours, in which medium oviposition takes place rapidly. These eggs have been collected and cultured, and laboratory-bred snails have been exposed to the miracidia, but so far no infection has taken place. This has of necessity been sporadic and no concentrated systematic attempts at infection over long periods have been possible.

1. Panagrellus silusiae was cultured in various media to determine the possibility of establishing it as a facultative parasite in the mammalian body. It was found to tolerate pH values of its environment between 1.0–8.5.

2. It survived for 24 hours in gastric juice but was rapidly killed by pancreatic juice. In both preparations larval mortality was higher than that of adults.

3. P. silusiae withstood environmental temperatures up to 87°C. At 40°C. death did not occur within 24 hours.

4. P. silusiae could survive without oxygen for at least 24 hours provided that the carbon-dioxide produced by its own respiration was not allowed to accumulate.

1. The lower intestinal tracts (duodenum to rectum) of 267 adult domestic fowls were examined for helminth parasites and 91% were found to be infested. The average numbers of worms and species present in infested birds were 240.6 and 2.42 respectively. Twelve species of parasites were recovered but only 5 occurred in more than 20% of the birds.

2. Twenty-six casualty and diseased chickens between 2 and 12 weeks old were examined. Fourteen were infested with helminth parasites and the average infestation was 499.9 worms of 2.79 species.

3. The total numbers of worms of all species present in individual fowls were shown to bear a relationship to the number of species comprising the infestations. Linear and quadratic equations which demonstrate the relationship have been derived from the observed figures.