REPORT OF THE COUNCIL. 427 



useful species has been more extensively studied with respect to the 

 size of the fish — the specimens being preserved and examined according 

 to size-groups differing by 5 cm. or 10 cm. In this way progressive 

 changes have been shown in the feeding -habits of various species as 

 growth advances. 



Certain seasonal changes have also been shown. The plaice during 

 the winter months have been found to abstain from feeding to a very 

 large extent. Thus the percentage of stomachs of this species found 

 empty has been found to vary from 99 per cent in November to 57 per 

 cent in February, although during the rest of the year the average 

 is less than 5 per cent. 



Bottom Fauna. — The invertebrates trawled or dredged on the 

 various expeditions prior to 1906 have been identified and recorded 

 with the exception of a few sponges and ascidians. The total number 

 of hauls examined amounts to 1129, of which 769 were hauls of the 

 large trawls and 360 special collections with small dredges and trawls. 



A beginning has been made in summarizing these data by means of 

 distribution -charts for the various species, the main object in view 

 being the delimitation, as far as possible, of definitely characterized 

 natural areas. The North Sea lends itself well to this work, as the 

 variety of species is relatively small, and a considerable portion of these 

 show fairly definite limits of distribution and centres of abundance. 



Bottom Deposits. — Out of 260 samples collected, nearly all (217) 

 have now been graded, with the object of showing the relative propor- 

 tion of fine and coarse particles in the deposits of different areas. For 

 this purpose the samples are shaken through sieves of successively finer 

 meshes, from 15 mm. to 0"5 nmi. in diameter. A striking result of 

 this sifting is the predominance of fine sand and its uniformity of 

 character over large areas of the North Sea. 



Herring Investigations. — In consequence of resolutions passed by 

 the International Council in 1905, increased attention has been paid 

 to the herring, and samples of this fish have been examined at Lowes- 

 toft during the past year at intervals of about a month or six weeks in 

 accordance with a prescribed scheme. Each sample consists of 100 fish, 

 the locality of capture of which is known ; and the characters of each 

 fish are separately recorded as regards (1) length, (2) number of verte- 

 brae, (3) degree of maturity, and (4) amount of fat. The samples 



