of the Fishery Boa/rd for Scotland* 



243 



is evidently a great want of systematic observations, and these 

 can only be carried on efficiently with some basis to work upon ; 

 the present list has been compiled in order to form such a 

 basis. It is hoped that every item in it may be checked repeatedly, 

 and that in course of time the many inaccuracies which doubtless 

 exist may be duly rectified. Notes have been added on those 

 species of fish eggs which are known to float ; most of these I have 

 been able to verify. The number of species of floating eggs will, 

 without doubt, be very much increased as our investigations are 

 pushed further. 



The spawning period of any given species may vary within 

 definite limits in different localities, and even in the same district 

 a considerable variation may be observed between one year and 

 another. The age of the individual, the supply and nature of the 

 food, the temperature of the water, the general severity or mildness 

 of the weather for some time previously', and many other points 

 have to be taken into consideration. Again, in some species, as, 

 for example, the herring, the spawning period is of short duration 

 so far as the individual is concerned. The majority of the eggs 

 are ripe about the same time, and are shed in a comparatively 

 short period. On the other hand, in such forms as the cod, the 

 period during which the eggs are shed by one individual is very 

 much longer, as only a few eggs are ripe at a time. This is a 

 point which, when carefully noted, may be expected to give 

 interesting results. 



The information given in the present list concerning the spawning 

 period of the Salmonidse is simply copied from Day's British Fishes, 

 As my friend Dr Day points out, this part of the problem is par- 

 ticularly difficult, on account of uncertainty existing as to what 

 should be regarded as a species, and what as a variety. Until this 

 point is settled any statistics would be imperfect and misleading. 

 It has also been shown that age, race, hybridism, and mauy other 

 factors have to be taken into account. Dr Day is collecting 

 information on this subject, so that until the publication of his 

 results, it appears better to let the matter remain in staH quo. 



