ARTIFICIAL HATCHING OF SPAWN. 55 



with salmon of from twenty to fifty days, and with 

 trout, even in the two apparatus employed here, there 

 was a difference of twelve days ; so that it will be 

 seen that it is difficult to set apart any particular 

 period as the distinct time consumed in incuba- 

 tion. Trout possibly may be held to go a somewhat 

 shorter period, because the great bulk of them spawn 

 rather later than the salmon — vast numbers of trout 

 not spawning until February, and many even as late 

 as March. 



On the 22d of February this year (1862), when 

 taking spawn in the Wandle, I saw scores of unspent 

 fish, and we could have obtained any quantity of 

 spawn we required. Water generally, therefore, will 

 of course be some degrees warmer than it was when 

 salmon were engaged in spawning, a month or so 

 earlier. I think it may be held, that while salmon 

 spawn from October to February, trout rather spawn 

 from November to March ; of course, instances may 

 occur foreign to this rule. Trout take a longer time 

 over the operation, and take a longer time to prepare 

 the redd, or spawning lied, than salmon. And the 

 preparing of the redd is often mistaken by those not 

 well informed on the subject for the act of spawning : 

 and fish are thus often caught at this time which are 

 frequently a week or ten days, or even more, from 



