LIFE-HISTORIES OF THE COD AND WHITING. 9 



stage commenced to take up its littoral habitat, and a rapid development of the external 

 pigment will give rise to the well-known ' tessellated ' condition. 



Whilst it is hard to correlate the characteristic pigment lines and markings in the 

 early stages with the environment, we are probably justified in regarding the recession 

 of the lower jaw and the forward movement of the ventral fins with the adoption of a 

 ground-feeding habit. 



If. The Whiting. 



The data for elucidation of the life-history of the whiting are not so abundant as- 

 those for the cod, but they are sufficient to enable us to determine, in a general way, 

 the form taken by the ontogenetic migration in this case. 



From observations at St Andrews and elsewhere, it has long been known that the 

 whiting has a very extended spawning period, from early March to the third week in 

 August. A study of the occurrence of the eggs in the Frith of Forth district gave a 

 period from the third week of February to the middle of July {Fifteenth S.F.B. Report, 

 p. 227). The whiting begins its spawning period at much the same time as the cod. 

 but whilst the latter does not extend beyond mid-May, the former continues till mid- 

 July. Hence with a spawning period of no less than five months, the young whiting 

 caught at any one time might be expected to show great diversity in size. 



A reference to Table III.* will show this to be the case. On 11th July 1895, 

 enormous numbers of young whiting were caught off' the Frith of Forth, which ranged 

 from 7 mm. in length to 56 mm. The greatest numbers occur at from 15 mm. to 38 

 mm., so that they form a maximum in the middle and taper off at each end. This also 

 agrees with the facts of the spawning phenomena, and there can be little doubt that we 

 have here a case of diversity in size, almost entirely due to a diversity in age, which in 

 its turn is due to a prolonged spawning period. Thus, whilst we would be inclined to 

 regard the whiting of 7 mm. as a few weeks old, that of 58 mm. might be five months 

 old as a maximum. 



The distribution of the eggs and spawning adults both tend to show that the whiting, 

 whilst differing in minor features, agrees in general with the cod in its spawning areas. 

 The egg is pelagic, and the life-cycle thus commences from much the same starting- 

 point as in the case of the cod. 



Up to the present there has been difficulty in obtaining the early post-larval 

 stages of the whiting. The larvae appear to be of normal surface-habitat, but on the 

 acquirement of the post-larval stage with free locomotion they appear to avoid capture, 

 and it is not till the length of 9 to 10 mm. that they are found with any frequency. 

 They then occur in the midwater far offshore. This would lead us to suppose that they 

 take an opposite course to the young cod, and instead of moving inshore they pass sea- 

 wards. Their occurrence in shoals is also very diagnostic. Thus in the table will be 



* See note I on page 3. 

 VOL. XL. PART I. (NO. 1). B 



