THE SALMON FAMILY. 277 



The actual bursting of the young Salnaon from the egg 

 is most interesting. The operation, which I have fre- 

 quently watched, takes place thus : — The fish lies in the 

 shell coiled round in the form of a hoop (as shown in fig. 1 



of the woodcut) ; and the greatest strain being at the back, 

 this is, of course, the first part to be freed. At this point 

 the shell splits across, and, after a few struggles, is com- 

 pletely thrown off with a jerk — leaving the red yolk of the 

 egg, by which the fish is nourished during the first five or 

 six weeks of its existence, suspended in a conical bag under 



land is from 100 or 110 to 140 days. South of the Tweed it is often 

 considerably less. In water of the constant temperature of 44°, eggs 

 have been hatched in 60 days ; whilst in some experiments made at 

 the Crystal Palace in 1859, several were actually matured in as little 

 as 30 days (see Report of Proceedings of Zoological Society for 1859, 

 p. 125). The eifect of differences of temperature upon ova cannot be 

 more curiously illustrated than by a fact mentioned by Sir John 

 Richardson, viz. that if entangled in the hair of an otter, or in the 

 feathers of an aquatic bird, an egg may be carried from one pool to 

 another without detriment, whereas the heat of the stomach of a warm- 

 blooded animal would arrest its circulation and destroy it. 



