[From the introduction]:
The purpose of this work was to study the effects of larval digeneans on the seasonal carbohydrate content and the reproductive biology of Littorina littorea L. at Scalby Rocks, North Yorkshire. Observations on infection with the different species of larvae were also made throughout the survey.

There have been many studies on the effects of trematode larvae on the carbohydrate content of their molluscan hosts, but in the main these have been based on histochemical tests and at isolated periods of time (see review by Cheng & Snyder 1962a). It was thought therefore that this aspect of host-parasite relationships afforded itself for further study from a quantitative and seasonal aspect.

This work falls into three more or less distinct sections; with an additional one which deals with the topography and ecology of the collecting grounds. The geology of the area is included in this to give a more complete picture of the nature of the coast.