On Abnormal Conditions of the Gills inMytilus edulis. Part I. On Permanent Natural Reversal of the Frontal Cilia on the Gill Filaments ofMytilus edulis

Abstract

A Heavy percentage of the mussels obtained from various parts of the Fal Estuary, during October and November, 1927, had the gills in an exceedingly abnormal condition (31.8% among 1488 recorded). Occasional mussels from other localities (Padstow, Teignmouth, Yealm, Saltash) have been observed to have slightly abnormal gills, though perhaps in the majority of these the condition was due to the presence of a large female pea-crab,Pinnotheres pisum. In the Fal Estuary mussels the abnormal conditions were doubtless correlated with some factor in the environment, the percentage of pea-crabs in these being so low (4–8%) that their presence could have no relation to the abnormal condition of the gills.