2 DR ARTHUR T. MASTERMAN ON THE 



the third week in February to the second week in May, with a maximum in early 

 April. 



The same proofs are to be obtained of the statement that cod, on the East Coast of 

 Scotland, spawn some considerable distance from shore outside the three-mile limit, 

 Prof. M'Intosh's statement to this effect being corroborated by Dr Fulton in examin- 

 ing the distribution of the spawning adults, and by the study of the distribution of the 

 eggs. We therefore know that the young larval cod commence their larval history 

 floating in the surface water, at or rather near the surface, at some considerable distance 

 from land. In the egg and early larval stages they would appear, by the nature of the 

 case, to be subject to the physical environment of currents, etc.; but on the assumption of 

 the post-larval stage, there is no reason why definite migration on the part of the young 

 cod should not be instituted. 



This was pointed out in 1884 by Prof. M'Intosh # in the following terms : — " It is 

 evident that the two areas, offshore and inshore, are dependent on each other, and that 

 legislation confined to one might not be followed by much benefit. Many inshore 

 grounds, for instance, depend on the offing for a supply of the eggs and young of the cod r 

 haddock, whiting, coal fish, and pollack ; whilst the offshore is fed by a variable stream 

 of the larger young of these fishes from the laminarian region of the inshore." By 

 drifting or by definite migration, or possibly by one method succeeding the other, such 

 an ontogenetic migration must be effected, for the ordinary habitat of the young cod, 

 somewhat over one inch in length, is inshore amongst the rock-pools. In the period 

 between hatching and this stage, the young must have effected a migration from the 

 offshore pelagic region to the inshore littoral. The details alone of this migration appear 

 to require determining. 



Prof. M'Intosh had in his possession a large collection of preserved material, 

 extending over several years, and consisting of various gadoids of the post-larval and 

 adolescent stages, and has kindly allowed me to go over them with a view to finding 

 diagnostic stages in the life-history of some of the gadoids, and, secondly, of elucidating 

 their early growth and migration. 



Table I.t contains a list of most of the specimens, arranged in size and order of 

 occurrence, which were identified as stages of the cod. It will be noticed that 

 there occurs a complete series of young forms, gradating no more than 1 mm. 

 between each, from 4 mm. to 46 mm., and that after this another series, varying no 

 more than 2 mm., extends to 60 mm. It is quite possible to figure the whole series, 

 but only in the very early stages is a repetition at intervals of 1 mm. found necessary - r 

 for the young cod, long before it reaches 46 mm., is well known. The stages of special 

 interest will be referred to later. The ontogenetic migration must of necessity be 

 gradual, and cannot be regarded as passing through its various stages with any absolute 

 lines of division. As in most natural phenomena, the majority of the species probably 



* Ifeport Trawling Commission, p. 76. t See note on page 3. 



