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Appendices to Fifth Annual Report 



this to be a well proved fact. It is probable, I think, that further close 

 examination of herrings during two or three more seasons might produce 

 sufficient examples to obliterate the small distinction. I am the more led 

 towards this view of the matter on account of the considerable amount of 

 what I have called individual variation. In so speaking I don't mean 

 that the variations occur altogether indiscriminately among the fish of the 

 same time and place of development and growth. It seems to me clear, 

 from the specimens examined, that to a certain extent peculiarities in the 

 shape of extreme variations of one or perhaps more characters, are found 

 common to several, perhaps a majority of the fish in one shoal ; but this 

 would be due to the circumstances affecting the development and growth 

 of these, and which, from so many other varieties being mixed up with them, 

 are almost sure to be modified in several directions in their descendants. 



In going through a prolonged and minute examination of these fish one 

 becomes much struck with the fallacies likely to arise by judging them 

 merely by a superficial or even careful ocular examination, without 

 recourse to actual exact measurement. The slightest difference in the 

 shape or size of some part — especially of the head and mouth parts — 

 sometimes causes such a change of appearance as to give rise to the 

 supposition of quite a racial distinction obtaining between two fish which, 

 on careful measurement, are found to be in all other essential principles 

 so alike as to prevent the acceptance of the theory of their racial difference. 

 This is well seen in the antorbital part of the head, where, in herrings of 

 similar size of head, body, &c, the minute difference of 1 to 2 mm. of 

 length in this part greatly changes the aspect of the head. It is also often 

 very striking where there is a very small difference in length or breadth of 

 the operculum, or even in the angle it holds to the head proper. But 

 there is one further and important cause of error where the general 

 appearance of the herring is taken, — as indeed appears commonly to be 

 done, — as a criterion of variety or race ; that is the condition of the re- 

 productive organs. According to the degree of development of these, the 

 herring may be greatly changed in form, and there need be little hesita- 

 tion in saying that many cases of apparent difference put down to racial 

 distinctions, e.g., between a short thick fish and one longer and more 

 slender in appearance, arises not from the fact that these belonged really 

 to a short and long variety, but that they simply had a more or less 

 deepened and thickened body due to nothing else than the condition of 

 the reproductive organs. These errors would be evident if the fish were 

 subjected to actual measurement in respect to every character. Especially 

 misleading are those varying conditions when present on fish which are of 

 different sizes and probably ages. 



This leads further to a reference to the mistake of supposing that 

 herrings are of a different race, because, after a single season's examina- 

 tion, they are seen to be in general size or otherwise, different from those 

 of another locality about the same time, or at different seasons. To 

 decide as to this effectually, continuous observations over several seasons 

 is essential, and I am conscious that in this respect my own observations, 

 although they have now extended over three years, are still insufficient ; 

 but at least, as I have shown in Part I., they indicate how changed, in of 

 course a limited degree, the herrings of one and the same locality, but of 

 different years may be. Much safer it is, where the difference between 

 individuals is so slight or so obscurely separated (as has appeared in this 

 investigation), as not to permit of a short examination clearly demonstrat- 

 ing its racial origin, to doubt rather than infer its accuracy. I feel pretty 

 sure that the variations just referred to are not permanent, but are due to 

 the varying conditions of food and temperature affecting the young 



