ON SMALLER PONDS. 167 



that time Mr. Maltby has allowed no jack to be put 

 into his water, as stock, above a pound in weight, 

 which (as younger fish do not gain weight so fast,) 

 will not increase in a year to more than about three 

 or four pounds. It is only after attaining that weight 

 that their growth becomes so astonishingly rapid, 



"In the lake at Boilsfut, jack, perch, and white 

 fish breed fast, but the fish born in that lake do not 

 increase so fast by two-thirds as those born in La 

 Hulpe; so that, although their transport from the 

 one to the other is expensive, yet it is made up for by 

 the increase of weight in the fish transported." 



These facts are both interesting and astonishing, 

 and are well worthy the attention of pisciculturists. 

 We have no record of jack growing at such a rate in 

 this country, and I believe the case is rather excep- 

 tional. 



Eoach, save as food for the jack, are worse than 

 useless in ponds, and should never be introduced 

 where there are carp, or they will in time exterminate 

 the carp : the roach increase so rapidly, and are so 

 much more active than the carp, that they wiU in 

 time literally starve the carp. I have had occasion to 

 note this on more than one occasion. I will instance 

 one. In Brownwich Pond, near Titchfield, in Hamp- 

 shire (a pond formerly belonging to a monastic insti- 



