Mr Shaw's Experiments on the Fry of the Salmon. 169 



sembling the tail of the tadpole extends from the dorsal and 

 anal fins to the termination of the tail. The ova, which, for 

 some time previous to being hatclied, had been almost daily in 

 my hand for inspection, did not appear to suffer at all from 

 being handled. When I had occasion to inspect the ovum, I 

 placed it in the hollow of my hand, covered with a few drops 

 of water, where it frequently remained a considerable time 

 without suffering any apparent injury. The embryo, how- 

 ever, while in this situation, shewed an increased degree of ac- 

 tivity by repeatedly turning itself in the e^g, an action pro- 

 bably produced by the increase of temperature arising from the 

 warmth of the hand. 



On the 24th of May (twenty-seven days after being hatched) 

 the young fish had consumed the yolk, but in a few days af- 

 terwards the whole of this family, with the exception of one in- 

 dividual, was found dead at the bottom of the pond, a circum- 

 stance which has occurred more than once in the course of my 

 experiments, arising, I apprehend, from a deposition of mud, 

 the same result having been more than once produced, when 

 the pond had not been sufficiently imbedded with gravel. 



To shew the eff*ect of increased temperature in hastening the 

 development of the infant fish, I may relate an experiment whicii 

 I made upon a few of the same ova, from which this family pro- 

 ceeded. On the 20th of April (106 days after impregnation) 

 finding the ova alluded to unhatched, and the temperature of 

 the stream being 41°, I took four of them and placed them 

 in a tumbler of water, covering the bottom with fine gravel, in 

 which I embedded the ova. I then suspended the tumbler 

 from the top of my bed-room window, above which I placed a 

 large earthen- ware jar, with a small spiggot inserted in its side, 

 from which I easily directed a stream of pure spring water in- 

 to the tumbler. The waste-water was carried out at the win- 

 dow along a wooden channel fitted up for the purpose. As 

 there was no fire in the bed-room, and the window facing the 

 north, the temperature did not range very high, 47° being the 

 average, while the average temperature of the water in the 

 tumbler was 45°. During the night, however, the temperature 

 would be very considerably increased, and tlie consequence was, 

 the young fibh in the tumbler were hatched in thirty-six hours, 



