Scientific Invesliijations. 5 



the majority of the indivrduals whicli compose a spawning-shoal 

 are pretty much of the same age, paiticuUirly if tliey vary only 

 slightly in size. If such a shoal be chosen, it will probably be possible 

 to determine the family variation accurately enough without 

 correction " (p. 88). 



" The herring is a species restricted neither to water of a 

 particular quality (salinity and temperature) nor to a specially fixed 

 kind of food " (p. x). 



All Heincke's " observations go to show that there must be 

 a close connection between tlie characteristic peculiarities of the 

 herring-race and the special physical and biological conditions of 

 its dwelling-place " (p. Ixxi). 



" The salinity of the water has long been regarded as having 

 the power of altering and limiting the form of marine animals " 

 (p. Ixxii). 



" x\.s a rule, races Avhich are geographically widely separated, or 

 better still, which are occupying regions whicli have physical dis- 

 similarities {i.e. dilTerent environment), differ more in certain 

 particulars than those which live together " (p. xxii). 



" In going from west to east the salinity of the sea-water of 

 the Baltic decreases, and this change is accompanied by a lessening 

 of the constitutional size of the spawning lierring, a reduction in 

 the number of vertebrae and in the breadth of the skull, a shortening 

 of the trunk, and increases in the lengths of the head and tail and 

 of the distance between the dorsal and ventral fins. Are these 

 significant peculiarities to be actually assigned to the direct or 

 indirect operation of the lowei'ed salinity ? " (p. Ixxii). 



" The herrings with the largest constitutional size, and with it 

 the greatest number of vertebrae, live on the coast of the northern 

 part of the North Sea, Norway, and Iceland. They are perhaps 

 exposed directly to the influence of the salt ocean water (of the Gulf 

 Stream). Is there here also a direct connection ? " (p. Ixxiii). 



" The herrings of the upper part of the Gulf of Bothnia may be 

 ripe when 125 mm. long " (p. Ixiv), whereas the smallest recorded 

 mature Scottish herring was 170 mm. long. 



" Herrings which grow up in very warm, shallow, brackish water, 

 and, for example, in the Schlei and Zuider Zee, have an extremely 

 low number of vertebrae to the first hajnial arch. Is this a direct 

 consequence of the special conditions under which the fry develop ? " 

 (p. Ixxiii). 



Heincke described the various races by means of measurements 

 made on the body. As many as sixty-three different characters 

 (p. T-l) were noted from time to time. The following characters 

 seemed to be of main value : — 



1. Total length, viz., RT. (Fig. 1). It is measured on the 

 principal axis of the body. The principal axis {Pa), is the line drawn 

 from the anterior point of the lower jaw, when the mouth is closed, 

 to the middle of the fork of the tail-fin. The end of the length- 

 measurement, viz., T, is the intersection of the principal axis by the 

 line at right angles to it. The latter cuts the lower ramus of the 

 tail (which has been spread out in its greatest natural extension) 

 a little in front of the apex, and passes the upper lobe a little behind 

 the apex. 



