ROE OF FISHES. 455 



Mr Hatchett made the curious remark that in the ova of those 

 tribes of animals, the embryos of which have bones, there is a por- 

 tion of oily matter, and in those ova whose embryos consist en- 

 tirely of soft parts, there is none. In what way the oily matter 

 contributes to the formation of bone, it is impossible, in the pre- 

 sent state of our knowledge, even to conjecture. Nor can any 

 source of the lime of the bones be pointed out except the shell. 

 And it would be very difficult to determine whether the shell 

 loses lime during the process of incubation. 



CHAPTER XL 



OF THE ROE OF FISHES. 



THE roe of fishes is well-known as the ovarium of that tribe 

 of animals. It consists of a congeries of very small eggs ; the 

 number of these in a single fish is remarkable. M. Petit found 

 342,244 in a carp of eighteen inches, and Leeuwenhoek states 

 the number in a cod-fish to be 9,344,000. Now, as each of 

 these is capable of producing a fish, we need not be surprised at 

 the immense numbers which swarm in the ocean and rivers, 

 notwithstanding the numerous enemies to which they are ex- 

 posed. 



The first set of experiments to determine the chemical nature 

 of the roe of fishes was made by Vauquelin on that of the pike 

 (Esox lucius) in 1817.* In 1823, M. Morin examined the roe of 

 the common trout ( Salmofario), and the carp ( Cyprinus carpio, 

 Linn.f) ; and in 1827, M. Dulong d'Astafort published a chemi- 

 cal examination of the roe of the barbel ( Cyprinus barbus, Linn.)J 



1. Vauquelin analyzed the roe of the fish in the following man- 

 ner : Four pounds of it were washed with water, till everything 

 soluble was taken up. The liquor being evaporated by the ap- 

 lication of heat coagulated into a white flocky matter, which, 

 when dried, was gray and brittle, soluble in caustic potash, and 

 precipitated by infusion of nut-galls and by nitric acid in white 

 flocks. It was albumen. 



When a portion of the coagulum from aqueous solution was 

 incinerated, it left a white alkaline ash, which consisted of car- 



* Jour, de Pharmacie, iii. 385. f Ibid, ix, 203, \ Ibid. xiii. 521. 



