Although much investigation has been made on the food of adult fish the information as to the food of the very young is scattered and fragmentary. It is the purpose of this paper to report on the food of a number of post-larval fish which have been examined fresh from the tow-nettings through the year 1917 from Plymouth Sound within the Breakwater and outside as far as the region of the Panther and Knap Buoys (about 2 miles from the shore) and occasionally from Cawsand Bay. The food of a number of preserved post-larval fish has also been investigated which were taken in the Young Fish Trawl in 1914 and reported on by Dr. Allen (1917).

It is only within comparatively recent times that it has been proved that the otoliths and scales of certain Teleostean fish can be used for the determination of their age.

Rings of growth, as they are called, are produced on these structures, and it is by counting the number that the age is ascertained, in much the same way as the approximate age of a tree may be determined by counting the annual rings.

It may perhaps be well to say that by maritime species are meant those Beetles whose habitats are covered by the sea for a considerable time during the flow and ebb of the tide. By sub-maritime species are meant the dwellers at high-tide mark or thereabouts, subjected to occasional wettings by the sea, and the species inhabiting brackish pools and wet places in salt-marshes. The coast species comprise individuals living under stones and rejectamenta, as a rule safe from the reach of high tide, and those peculiar to the roots, leaves and flowers of plants attached to the coast, as well as inhabitants of wooden piles on the shore and the denizens of the ooze of fresh-water trickles on the cliffs—excepting species equally obtainable inland.

On May 30th, 1916, a number of large Buccinum undatum were brought in from the trawling grounds ; 40 of these were examined and 34 were found to contain larval Trematodes. Another lot in the spring of 1917 contained about the same percentage of infected Mollusks. Two species of Trematodes were present, both contained in the digestive gland, which was absolutely riddled with them.