INTRODUCTION. XXV 



which fish could be admitted. This curious fact has been 

 confirmed to me by Colonel Sykes and other observers who 

 have lived long in India, who state that the tanks and ditches 

 near fortifications are alternately filled and empty on the oc- 

 currence of every rainy and dry season, but that a few days 

 after the commencement of each rainy season these tanks and 

 ditches are replenished not only with water, but also with 

 small fish. The solution appears to me to be this. The 

 impregnated ova of the fish of one rainy season are left un- 

 hatched in the mud through the dry season, and from their 

 low state of organization as ova, the vitality is preserved till 

 the occurrence and contact of the rain and the oxygen of the 

 next wet season, when vivification takes place from their joint 

 influence. If this solution of the problem be the true one, 

 it points at once to what perhaps may be effected after a 

 few experiments, namely, the artificial fecundation of the 

 roe, the drying of that roe, (or of other roe naturally im- 

 pregnated,) sufficiently to prevent decomposition, and its pos- 

 sible transportation to, and vivification in, distant countries. 



The growth of young fish is rapid in proportion to the 

 size of the parent fish, or the ultimate size attained by the 

 species. They appear to be liable to occasional malforma- 

 tion, and two instances are figured, vol. i. page 110, and 

 vol. ii. page 59, and a third of the same kind has been seen, 

 where the upper jaw is deficient in the requisite length. 

 Hervey is said to have been the first who observed that most 

 irregularities in human structure were to be found in the 

 lower animals, and modern physiologists have shown that 

 various gradations of structure permanent in the lower ani- 

 mals are successively assumed by those of higher organiza- 

 tion in their passage towards their ultimate developement. 

 These usually transitory conditions sometimes become per- 

 manent, and constitute monstrosities. The most frequent 



