Scientific Investigations. 



21 



which a pin is inserted. Tlie pin is taken as the position of the 

 point. 



XXVII. The point where the dorsal edge reaches its greatest 

 height above the principal axis. 



XXVIII. The height above the principal axis at this distance is 

 measured by dividers. 



XXIX. The point where the ventnim reaches its greatest depth 

 below the principal axis. 



XXX. The depth below the principal axis at XXIX. measured by- 

 dividers. 



Nos. XXVIII. and XXX. together give the depth of the fish. 



Skeleton. 



XXXI. The upper length of the skull, i.e. the distance from the 

 front vertical edge of the etlimoid to the hind upper edge of the supra- 

 occipital bone, viz., Icr, Fig. 2. 



XXXII. Greatest breadth of skull, viz., Itcrof. Fig. 2. 



Nos. XXXI. and XXXII. are measured by means of callipers. 

 The length divided by the breadth of the skull is the index of the 

 form of the skull. 



XXXIII. The number of vertebrse. The last vertebra is B in 

 Fig. 7 . Not ? = Notochord ? 



Fig. 7. — Diagram of Tail-hones 

 of Herring. 



XXXIV. The number of the vei'tebra bearing the first haemal arch. 



XXXV. Weight (Grammes). 



XXXVI. Colour of the flesh. 



The measurements are to be converted into percentages of the 

 length of the fish. All the measurement-characters of a fish are con- 

 verted into percentages by multiplying them by the same factor, viz., 



i — — j — j-ju — ^^T" This is readily accomplished by means of Crelle's 



tables. 



The average of the percentages for each character is to be calcu- 

 lated. 



