720 pisces. 



The sexes in fishes are, in the greater portion, in separate individuals. 

 The ova are generally impregnated by the male after extrusion, and the 

 young are developed without the care of the parent. The male is known, 

 besides other distinctions, by the presence of the testes, or milt, and the 

 females by the ovary, or roe, which both occupy the same relative place in 

 the body of the animals. Those are said to be viviparous, in which the ova 

 are matured, and the young developed before extrusion. In the develope- 

 ment of the embryo, the heart first appears, afterwards the spine, eyes, and 

 tail. Of the organs of motion, the pectoral fins first appear, followed in suc- 

 cession by the caudal, dorsal, and anal fins. Among the oviparous fishes, 

 hermaphroditism was long considered as a rare and accidental circum- 

 stance. Baster noticed this occurrence in the whiting, Duhamel in the 

 carp; Haller gave his testimony to facts of the same nature; and Pallas 

 believed that the genus Syngnathus had no males. Lastly, Sir Everard 

 Home, in the Philosophical Transactions for 1815, states the same fact re- 

 garding the lampern or pride, and the Gastrobranchus caucus of Bloch. 



The amazing reproductive powers of fishes are well known. In the ovary 

 of the ccd in December, were formed three millions six hundred and eighty- 

 six thousand seven hundred and sixty ova ; in the flounder in March, one 

 million three hundred and fifty-seven thousand and four hundred ; in the 

 herring in October, thirty-six thousand nine hundred and sixty ; and in the 

 tench, three hundred and eighty-three thousand two hundred and fifty-two. 

 And Bloch relates, as the result of an experiment, regarding the productive 

 power of the carp, that, in a pond of seven acres, in which were placed four 

 males and three females, the increase in one year was one hundred and ten 

 thousand young carp, a number too great for the size of the pond and the neces- 

 sary supply of food. But this astonishing capability of increase is modified by 

 a thousand circumstances, which regulate the number produced to the supply 

 of food. Myriads of these ova form the food of different species; and myri- 

 ads more of the young may be supposed to be destroyed in an element 

 where almost all are destined to become the prey of one another. Notwith- 

 standing these deductions, however, the importance of this class as an 

 object of commerce, and as a supply of food, holds out an inexhaustible field 

 for the enterprise of nations whose territories approach the sea. Of the 

 migrations of fishes, and the causes which prompt these annual influxes of 

 certain fishes, on certain coasts, little is with certainty known. Probably 

 they are regulated by the same causes Avhich influence the migrations of 

 birds, to find food and proper places for reproduction; and the same instinc- 

 tive impulse which induces the salmon, at certain seasons, to ascend rivers, 

 may bring myriads of fishes to the shores for a similar purpose Little is 

 known with regard to the comparative age of fishes. The carp has been 

 known to reach two hundred years, and the pike to two hundred and sixtv i 

 and if whales be found of less size now, than in former ages, when their 



