MARINE BIOLOGICAL STATION AT PORT ERIN. 129 



There are, however, four species inhabiting Manx waters, 

 and the Worm Pipe-fish (fig. XXYL, 3), which lurks under 

 stones and amongst the weeds at low tide, is generally to 

 be seen in the Aquarium. Like its relative the Sea-horse, 

 it is fond of twining its tail around sea-weed, and will 

 remain in such a position almost motionless for a consider- 

 able time. It swims gracefully by the rapid vibration of 

 its dorsal fin. When the female Pipe-fish extrudes her 

 eggs the male receives them into a pouch on the under 

 surface of his body, and there retains them until the 

 young are hatched. 



Flat-fishes (Fig. XXIX.). 



This is a most important family from the economic 

 point of view, as it includes such valuable food fishes as 

 the turbot, sole and plaice. It is also of exceptional 

 interest to biologists on account of the curious 

 metamorphosis which transforms the symmetrical, evenly 

 developed young fish into the flattened, unsymmetrical 

 adult. The body of all these fishes is flattened from side 

 to side, and the darker coloured side on which the eyes are 

 situated is not the back of the fish, as many people 

 suppose, but usually the right side. Exceptions to this 

 rule are found in the turbot, brill, megrim, and the top- 

 knots, in which the left side is uppermost, is coloured, and 

 bears the eyes. The plaice [Pleuronectes platessa) may be 

 readily distinguished by the red spots on its upper surface. 

 The lemon-sole (Pleuronectes micro cephalus) has the upper 

 surface clouded and blotched with dull yellow and brown. 

 The mouth is smaller and the lips thicker and more 

 rounded than those of the plaice. The common dab 

 {Pleuronectes limanda) bears considerable resemblance to 

 the plaice in general outline, but it is a much smaller fish, 

 and the upper surface is brownish and has no red spots. 



