show principally that the younger half grown cod are present on the shallower North 

 Sea banks the whole year round»'. The recaptures of cod in the present experiments illustrate 

 this statement, with which they are perfectly consistent. There is no indication of a 

 seasonal migration. The four cod recaptured in summer from experiment 31 have all 

 moved southwards, but not appreciably beyond the edge of the Dogger Bank, on which 

 they were set free. It is however worthy of notice that southward and westward move- 

 ments were shown by most of the fish recaptured, at all periods of the year, except 

 perhaps the spring. Out of 11 records of travel exceeding a distance of 30 miles from 

 the place of liberation, eight were between S and W, one SE, one NW, and one a little 

 north of East. 



Prof Henking considers that the cod showing marked migrations in the North Sea 

 are those of over 60 cm. in length 2. Twenty-two such fish were marked. Of these 

 but one was recovered, namely cod no. E. 3.04 from Experiment 8, on the Dogger Bank. 

 This, in accordance with the above conclusion, was found in September in deeper water 

 (30 fathoms). A few other fish attained 60 cm. during their period of freedom. Of these 

 E. 8378 (Exp. 33) and E. 8269 (Exp. 39) show some approach to the tendency to seek 

 shallow water in winter, deeper water in spring, to which Prof Henking alludes, while 

 E. 34. 04 (Exp. 19) and E. 6742 (Exp. 25) have not greatly changed their ground. All 

 these fish however are only just large enough to be included in Prof. Henking's class of 

 larger fish. 



Rate of growth. Twenty fish were recaptured after periods of at least a fortnight, 

 and returned in a condition which allowed of their being measured, no injury due 

 to the marking being noticed. The following table gives the initial length of these 

 fish and their monthly growth; the latter is given to the nearest millimetre without 

 allowance for shrinkage after capture. The month is taken as 28 days. 



A point of interest in the table is the low monthly growth generally shown by fish 

 which have been only a month or less at liberty. This is no doubt due, at least in 

 part, to the effects of the drying of the fish after death. As the cod dries, its length 

 decreases by an amount which unfortunately is not known; and this shrinkage, while 

 not very considerable when compared with the growth of several months, naturally causes 

 a much more serious diminution in the growth apparently occurring in one month or 

 less. It is not impossible however that the growth of the cod during the first month 

 of its regained liberty is retarded while the cod is recovering from the effects of trawling 

 and marking. 



The mean monthly growth of the 15 cod which had been at liberty for at least 3 

 months was 1-5 cm. 



Conclusion. Summing up the results of these experiments, one sees that 252 cod 

 were marked on the Dogger Bank and the grounds to the South and West of it at 

 various seasons of the year, November, December and January being alone unrepresented. 

 42 fish were returned, and the scarcity of recoveries during the second six months from 

 liberation leads to the conclusion that the methods used in marking the fish were im- 

 perfect, especially as regards retention of the labels. Judging from the returns of the 

 first six months about a quarter of the fish marked should have been caught in a year. 



I Rapports et Procès Verbaux. Vol. III. 1905. Appendix G. p. 38. 2 Rapports et Procès Verbaux. 

 Vol. III. 1905. Appendix G. p. 39. 



