of the Fishery Board for Scotland. 



223 



decision, however well founded it may appear. It lias been found gener- 

 ally, and also in this particular case, that mere theory often has had to 

 give way to the light of practical experiences and those thereon established 

 facts. It was in recognition hereof that sea-hsh hatching was taken up in 

 this country, and it must therefore necessarily be judged on its own merits ; 

 but in order to do so the work must be subjected to a just trial and enjoy 

 a fair chance. The fry produced in the Hatchery is at present being dis- 

 tributed in a relatively closed area of the sea in order to find out what 

 effect the artificial fish culture may have upon the abundance of fish there. 

 But owing to the incomplete condition of the station, this experiment has 

 had to be confined to one single place (Loch Fyne), while it ought to be 

 extended to several lochs or closed areas before the experiment can be 

 considered a true test of the work. This is clearly so, because permanent 

 or temporary physical conditions in any one particular place may be un- 

 suitable for the development of an increased stock of fish, and this would 

 perhaps only be found out by comparison with the results obtained in the 

 various places. But such a conclusive test of fish-hatching in the present 

 case can only be carried out when the number of fry produced is increased 

 and as this can be accomplished without an increased working expendi- 

 ture, I hope that the proposal for these necessary improvements in the 

 2iear future will be given a favourable consideration. 



4. Preliminary Notes on Continued Eearing Experiments with 

 Larval and Post-Larval Plaice and Lemon Sole. 



In a paper " On the rearing of the larval and post-larval stages of the 

 plaice and other flat fishes,^* published in last year's Report,"^ I described 

 an experiment in the rearing of plaice through the post-larval stage, at 

 the end of which the young fishes had the form and habits of the adult. 

 In that paper it was mentioned that the greater number of the young fry 

 which were placed in the hatching jars did not take any food, though such 

 was present in abundance, but died from starvation. Others, again, took 

 the food regularly and developed quickly. In referring to this peculiar 

 circumstance I then made the suggestion that the fry might have been 

 retained rather long in the hatching apparatus without food. In similar 

 experiments which were carried out in the spring, 1897, the same peculi- 

 arity occurred. Some larvae were successfully carried through the post- 

 larval stage, but the greater number was lost in the same way as on the 

 first occasion. 



In all these experiments I had been acting upon the general belief that 

 the larval plaice is nourished by the yolk only until this is absorbed, and 

 at that stage I had placed them in the rearing jars and supplied the food. 



By watching the process of the absorption of the yolk from the moment 

 of hatching onwards I observed that the diminishing of the yolk appeared 

 proportionately greatest soon after hatching, or that the amount of yolk 

 absorbed daily was far greater in the beginning of the larval stage than 

 later. I particularly noticed that the last portion (about one quarter of 

 the total mass of yolk) was only reduced very slowly. If the rate of 

 development of the plaice is reduced towards the end of the larval stage, 

 it is probable that less nourishment will suffice ; but if this is not so, it 

 becomes evident that more nourishment is required, and possibly of a 

 different nature, than what is simply provided by nature directly and 

 attached to the fish in the form of yolk. It would undoubtedly be wrong 

 to reason that the last remnant of yolk was absorbed before the first 



*Fifteeuth Ann. Rep. of the Fishery Board, Part iii. , page 175. 



