THE SAND-EEL FAMILY. 309 



from a young sand-eel which was caught with a great number 

 of its companions in the bottom-net, at the end of April. This 

 stage represents the termination of the bottom-habitat and the 

 commencement of the journey upwards through the mid- water 

 to the surface. There is little change in the pigmentation from 

 the previous figure. A row of brownish-black pigment-spots 

 (about a dozen) run along the dorsal wall of the abdominal 

 cavity, on either side of the intestine, and there are traces of a 

 ventral row, continued onwards from the vent to the tail. The 

 median fin is continuous, from the neck round the tail to the 

 belly. The notochord may be seen to be deflected dorsally 

 at its caudal termination and the lower fin-rays are conspicuous. 

 The vent opens at a point three-fifths of the length from head to 

 tail, and this feature forms the only really conspicuous distinc- 

 tion between the young sand-eel at this stage and the young 

 herring of about the same length. We have no reason to 

 believe that the sand-eel and the herring are genetically allied, 

 but we shall see (cf Herring) that the whole series of phe- 

 nomena connected with spawning, larval migrations, etc. are 

 closely alike, and it seems reasonable to seek in this the cause 

 of the structural resemblance of the young stages. 



Almost immediately after this stage the young sand-eels 

 migrate through the mid-water upwards to the surface, till we 

 find during April and May countless numbers of young sand- 

 eels from 12 millimetres (^ inch) upwards sporting themselves 

 in the surface-water. They seem to abound some miles out 

 from the east coast, examples being obtained from off the Isle 

 of MayS Aberdeen, Montrose and Stonehaven. These little 

 sand-eels are found in great numbers in the stomachs of food- 

 fishes, and doubtless are very delicate morsels. 



The young sand-eels in May are found in the surface-water 

 in millions. There are in the St Andrews Laboratory four jars 

 of these May post-larval forms, taken 15 miles off Aberdeen, 

 Montrose, and Stonehaven, and their number may be estimated 

 at about 50,000. 



Thus the young sand-eel forms a very important supply of 

 food to other fishes, both in its early post-larval stage, when 

 1 Vide W. 0. M. Trawling Report, 1884, p. 360. 



