46 Fishery Board for Scotland. 



some of the material had been preserved in formalin for a number 

 of years Coscinodiscus could still be identified lying in the intestinal 

 tract in a number of the specimens. 



The comparatively rich collections of plaice larvae from stations 

 in the Moray Firth in January 1905 is extremely interesting and 

 agrees with the condition found for the early appearance of the eggs 

 in that spawning year. Spawning season 1904-1905 was an early 

 one in that locality, and the eggs from which these larvae had hatched 

 out may have been spawned in the last days of November or early 

 in December. The appearance of such a large number of larval 

 forms at Station 30 thus early in the season is also significant as it was 

 shown that eggs in the later stages of development also appeared 

 early at these offshore stations, earlier, in fact, than the newly spawned 

 eggs. Both the eggs in the later stages of development and the 

 larvae at the offshore stations must have been derived from an earlier 

 spawning area, and the only area which has been shown to be earlier 

 is the Dornoch Firth. 



Similarly, in March 1906, at Troup Head and Kinnaird Head, 

 where the percentage of eggs in the later stages of development was 

 high, hatched out larvae were found before larvae had appeared in 

 the plankton at Lossiemouth, which is a much more important spawn- 

 ing ground. These facts help to confirm the view that there is an 

 alongshore drift eastwards of eggs and larvae from Lossiemouth, 



It is known that the plaice after metamorphosis finds a suitable 

 habitat on shallow sandy flats, and that such favoiuable localities in 

 Scottish waters occm' only on the very margin of the coast. The 

 advantages of this habitat to the species have been aptly put by Dr. 

 Fulton : — " The selection of this habitat is clearly of advantage to 

 the species in summer, since it is the region of maximum warmth, 

 but it is curious that the beach should still be frequented in winter 

 when it is the coldest region ; for although the larger individuals 

 and some of the others appear to withdraw to slightly deeper water, 

 they may still be procured on the beach in considerable numbers. 

 There is probably a greater advantage to the species by the com- 

 parative immunity from enemies which the situation confers, since 

 few piscivorous fishes venture into shallow water unless in exceptional 

 circumstances." 



It is desirable, even at this stage, to enquire how far the study of 

 the distributions of eggs in thfe various stages of development provides 

 information as to the conditions as well as to the localities in which 

 the tiny larvae are hatched out. Are the chief spawning places such 

 that, when the bulk of the larvae appear from the egg, they find 

 themselves in the immediate neighbom'hood of a locality suitable 

 for development ? To what extent do the prevailing physical con- 

 ditions assist the passive eggs and helpless larvae in securing a suitable 

 habitat for further development ? It is of vital importance to the 

 species that there should be an intimate connection between the 

 spawning grounds and the localities suitable for growth. 



It is known that as the tiny plaice grow they gradually migrate 

 seawards to deeper waters, and from a knowledge of these movements 

 Heincke has been able to formulate the following law of distribution 

 for the plaice : — " The size and age of the plaice in a definite part of 

 the North Sea are inversely proportional to the density of their occur- 



