The investigation here described may be regarded as the natural sequel of the observations by which I showed that the plaice of the Brown Ridges, as well as those from the Plymouth grounds, were smaller when they attained to sexual maturity than those of the northern part of the North Sea. Mr. Holt, in 1894, published in this Journal some observations on the dwarfed and ciliated or spinulated plaice of the Baltic; and Dr. Heincke, now Director of the German Biological Station at Heligoland, had suggested as a probability that the plaice of the Heligoland region were a smaller geographical race, distinguishable by special characters from those of other regions. I referred to this subject at the end of my paper on the Physical and Biological Conditions in the North Sea, in the preceding number of this Journal, and mentioned the paper in which Georg Duncker has recorded and discussed the results of an examination of samples of plaice and flounder from various localities.