48 DEPARTMENT OF THE NAVAL SERVICE 



These percentages are calculated from very large quantities, in 1913 for instance, 

 1,222 litres, about 550 millions of eggs, and they do not vary greatly from year to year. 

 When much brackish water occurs on the coast, the mortality may inci*ease considerably ; 

 this is, however, rarely of long duration. Similarly, if the weather for any length of 

 time is dark and cloudy, the eggs may become entirely overgrown with bacteria, from 

 which, however, they may be freed by being placed in a bath with water of high salinity. 

 As to the degree of influence exerted by these bacteria (Leptothrix?) in a natural 

 state I can say nothing from experience; possibly the conditions at the hatchery may 

 be especially favourable to them. 



As regards the growing up of the young, we have here to consider another factor, 

 viz., that of nourishment. That this is of great importance to the growth of the 

 young is certain, and possibly the most critical period of all in this respect is the 

 time when the young first commence to take food; they do not live long without 

 nourishment after the yolk-sac has been consumed. 



In the spring of 1914:, a number of newly hatched young were placed under 

 observation at Flodevigen for the purpose of ascertaining when they commenced to 

 take food, and what such then consisted of. The investigations were carried out by 

 Prof. H. H. Gran, and led to the result that the young did not take any food mitil 

 the yolk-sac had been absorbed, and that on commencing to feed, they appeared from 

 the first to prefer animal matter, such as mollusc larvse, nauplii, etc., seeming, strangely 

 enough, to despise the innumerable diatom forms which are likewise present in the 

 water. 



Such food as was pumped in with the sea water was alone available to the young 

 fish; but as the greater part of the plankton was retained in the apparatus, the 

 nutritive matter was fairly concentrated there. 



As to the influence exerted by conditions of nourishment upon the growing of the 

 young in a natural state, this question has not yet been investigated, and it will 

 probably form one of the earliest subjects for future fishery investigations. 



It is, we may say, of prime importance in every way to ascertain what factor or 

 factors normally hinder the germs of our most important fish in their development, 

 to discover at what stage the destr\iction occurs, and by what means it takes place. 



This will have to be done by investigation of the propagation of fish in the sea, 

 and by experiments and artificial culture, both branches of the work proceeding in 

 conjunction. 



It is from such a point of view that I have in the foregoing pages endeavoured to 

 treat the material of fish eggs and young collected by the Canadian expedition. Unfor- 

 tunately, however, we still know far too little of these questions, and my work can 

 therefore only be regarded as furnishing, in this respect, a preliminary survey of the 

 complicated, yet highly interesting, conditions which prevail on the Atlantic coast 

 of Canada. 



LITERATURE. 

 Alexander Agassiz. 



1878. I. On the Young Stages of Bony Fishes. 



1882. III. On the Young Stages of some Osseous Fishes. 



Jordan and (xilbert. 



1882. Synopsis Fishes of North America. 



E. W. L. Holt. 



1891. On the Eggs and Larvae of Teleosteans. 



1893. On the Eggs and Larvae and Post-larval Stages of Teleosteans. 



(The Scientific Transactions of the Royal Dublin Society, vols. IV 

 and V.) 



