RAPPORTS. XIII C4: MASTERMAN — 16 — 



author attempts a correlation between fecundity and length and fecundity and age.. From 

 his- curves, he shows • that the fecundity increases, with length and also increases with 'age. 



Beyond this it appears scarcely safe to go though the author attempts to draw the 

 inferences that the no. of eggs, for the same, age increases proportionately as the square 

 of the length and for the same length increases in direct proportion to the age. 



The data seem insufficient for such deductions. No question of age appears to enter 

 into the correlation of length and fecundity and none of length in that of age and fecundity, 

 and no figures are given of individuals of the same length at different ages. 



The data may perhaps be said to suggest such a relation, but it is clear tha 

 much more extensive data are required. 



The Baltic fish appear to be more fecund for the same length and less fecund for 

 the same age, than those from the North Sea. ' The former are known to have a slower 

 rate of growth than the latter. 



The definite establishment of a law of fecundity in relation to length and to age would 

 be an important step towards the reduction of fish problems to mathematical treatment 

 and combined with length frequencies might give a valuable estimate of the powers of 

 maintainance of a species. 



The Food of Fish.' 



Intimately connected with the length or weight frequencies of fish is the question of 

 their food. 



In the paper under review Franz summarises the observations on the Food of Fish 

 made at the Helgoland Biological Laboratory. The actual observations were made by 

 various people — Bolau, Heincke, Richard etc. , , . 



In all but a fe\y cases (in. Plaice and Dabs) however he only giyes a , list of the 

 species found in the stomachs with no information as to their relative abunda,nce (except 

 in a few cases where only one specimen was found) nor as to the locality, date, size or 

 number of the fish examined. , 



As regards the nature of food, his lists show considerable similarity to the previous 

 observations of Todd.^ 



Certain species (Cod, Dab and Paice, especially the last named) he treats in more 

 detail. 



Dab. Pleurojiectes limanda — Fran? has examined the food of the first bottom 

 stages and finds that the difference between that and the food of the older fish is not so 

 striking as in plaice. He confirms the fact that as Todd has already shown, Plaice and 

 Dabs are not competitors for food and cites a single example. He suggests that dabs 

 find their food hy. sight, plaice by touch, and points out that aquaria observations show 

 the dab to have the sharper sight. , 



Pleuronectes platessa — This important food-fish is treated in considerably more 

 detail than any of the others, chiefly under the heads, Food and. Age, Food, Foodgrounds, 

 Food and time, pf, day, and Food migrations (?). 



> 1 am indebted to Mr. R. A. Todd of the staff of the Board of Agricufture and Fisheries for help and 

 criticism on this work which is kindred to his own. A.T. M. 

 2 R. A. Todd. 



