Plankton Research at Plymouth

Abstract

THE May number of the Journal of the Marine Biological Association is devoted to an interesting account of the investigations of the plankton of the sea outside Plymouth Breakwater, made during the year September, 1915, to September, 1916. The main systematic research has been conducted by Miss Lebour, while Dr. Allen describes post-larval stages of fishes, and Mr. Matthews gives an account of the variation in the quantity of phosphoric acid present in the sea-water. Miss Lehour used Lohmanns method of centrifuging small volumes of sea-water (50 c.c.), and then actually counting the organisms so obtained. Her results are in general agreement with those of Lohmann (at Kiel) and Herdman and Scott (at Port Erin). There are well-marked seasons of abundance of microplankionic organisms, diatoms occurring in greatest quantity some time in the spring or early summer, and then again in the autumn, while Pendiniales attain their maximum of seasonal abundance a little later than the diatoms. The Peridiniales have been very thoroughly investigated, and Miss Lebour describes eight species which are new to science and twenty-one species which have not hitherto been recorded from British seas. She also gives some records of the occurrence of larval Trematodes, free-swimming in the sea, and descriptions of the Helminth parasites of Sagitta. These worms have been noticed many times, and some of them are very familiar to planktologists, but no sound identifications have been made prior to the research now under notice. Sagitta is a host for larval forms of Derogenes varicus and Pharyngora bacillaris, both well-known fish Trematodes. A larval Ascaris also occurs, and two larval Cestodes, the species of which are not identifiable.