238 



Part III. — Sixteenth Annual Report 



Data of Collection, Distribution, tfec. 



A large number of specimens were omitted from these data, either 

 because they were doubtful or belonged to other species. The doubtful 

 specimen;? were mostly in the early post-larval stage, from 3mm. to 6mm. 

 Sufficient remain, however, to illustrate the main facts of distribution. 

 The distribution of these post-larval forms is connected, on tlie one hand, 

 with the spawning areas of the adults and the distribution of the eggs ; 

 on the other hand, with the migrations and distribution of the immature 

 fish. 



Dr. Fulton,* in the 15th Annual Report of the Scottish Fishery Board, 

 has described the results of the experiments on currents which were 

 carried on for some years on the east coast of Scotland. In this paper 

 (p. 334) he shows that the distribution of the eggs, larval and early post- 

 larval stages, is due to the existence of currents, tending in the main, and 

 for the greater part of the year, in a southerly direction along the east 

 coast of Scotland. These are surface currents, probably extending down 

 to at least 6 or 7 fathoms, but it is quite possible that the whole depth 

 of the water has a similar movement. Certain influences cause variations 

 at particular places and seasons. " In confined areas, like the western 

 part of the Moray Firth and the Firth of Forth, the movement of the 

 surface water is irregular, and depends upon variations in the winds and 

 tides." 



The distance over which the eggs will drift depends upon the length 

 of time the young embryo is in the egg, other things being equal, and 

 the time taken to pass through the larval and early post-larval stages. 

 Only for one form, the plaice, has this period been determined; and Dr. 

 Fulton, reasoning from this, thinks that the eggs of the plaice may travel 

 50 miles or more, and that the young plaice found on the sandy beaches 

 may be from 60 to 100 miles from the spawning ground of the adults. 



In the same number of the Reports, Professor Clevef, of Upsala, gives 

 a short sketch of a theory on the distribution of currents. These 

 currents are characterised by different marine organisms, crustaceans, 

 diatoms, flagellates, etc. 



The importance of this theory lies in the aid it gives to the under- 

 standing of what becomes of the post-larval stages. If the eggs and 

 early post-larval stages are subject to drift, the late post-larval stages are 

 admitted by Dr. Fulton to be able to look after themselves. When 

 these young forms come into inshore waters it is found, as will be shown 

 by the data, that there is a complete separation of these species from one 

 another. These currents may have something to do with this separation, 

 in addition to the inherited tendencies in the diflerent species to seek 

 different habitats and different food. 



Plaice. 



Date. 



Net. 



Place. 



Number of 

 Specimens. 



Length in 

 mm. 



April 3, 1893 



Midwater 



East of May, 



1 



12 



„ 16, 1887 





St Andrews, 



1 



12 



„ 17, 1895 



5 J 



Station I. , Forth, 



2 



12, r2"5 



23, 1888 





St Andrews, 



8 



Larval. 



„ 26, 1889 



J> 





1 



Larval. 



„ 28, 1887 





4 fathoms. 



2 



10, 10-5 



„ 19, 1895 



Bottom 





1 



8-5 



„ 25, 1890 



J5 



Station VII., Forth," 



1 



9 



* The Currents of the North Sea, etc., p. 334. 

 t Report on the Phyto-Plankton, etc., p. 297. 



