302 



Part III. — Eighteenth Annual Repwt 



In this research all the measurements have been made on the left side 

 of the fish. 



Vertebra and Fin-rays. 



In the enumeration of the vertebrae no difficulty presents itself ; the 

 same is true of the fin-rays, with the exception of those of the first dorsal 

 fin. The posterior rays of this fin are, as Garstang has pointed out, very 

 small, and often do not appear above the skin. It is necessary to 

 dissect the floor of the dorsal groove in every fish ere one can be sure 

 that all the fin-rays have been noticed. In many cases only the base is 

 found as the representative of the ray. This, however, has been 

 included in the number of rays. 



The Mackerel Investigated. 

 The mackerel were obtained from three localities : — 



I. Clyde — Lower Loch Fyne, June and July 1899 — 171 fishes ^ 

 „ Kilbrennan Sound, October 9th „ 12 „ J 

 II. Barra June ,, ,, 65 ,, 1 



Stornoway August 13th „ 23 ,, J 



III. Aberdeen August and September, 



The mackerel from Lower Loch Fyne were taken in mackerel nets ; 

 those procured from the other districts were captured in herring drift- 

 nets. 



The following Table (II.) shows the sizes and numbers of the fish 

 examined. They have been arranged in centimetre divisions. All the 

 fishes, for example, measuring from 30 to 30*9cm. are entered in the 

 30cm. group, and. similarly with the others. 



Table II — Sizes and Sex of the Mackerel Examined. 



183 



207 



Size. 



Aberdeen. 



Inches 









(approxi- 



Cm. 





? 



mate). 









10 



26 









27 







11 



28 









29 



1 



1 



12 



30 



3 







31 



11 



5 





32 



21 



15 



13 



33 



32 



32 





34 



31 



19 



14 



35 



8 



20 





36 



2 



2 





37 



3 



1 



m 



38 









39 







LG 



40 









41 









42 







17 



43 







Total, - 



112 



95 



Clyde. 



3 

 f) 

 5 

 3 

 9 

 10 

 22 

 17 

 11 

 4 



9 



91 



1 



3 

 3 



5 

 12 



6 

 16 

 25 

 12 



1 



4 



9 



90 



Barra and 

 Stornoway. 



1 

 1 

 1 

 6 

 3 

 11 

 2 

 1 

 1 



1 



2 



1 

 1 

 2 

 1 



35 



1 



3 

 4 

 10 



4 



9 



42 



11 



