G Observations on the Thrce-Spined Stickleback. 



fry that had died in the hatching, into his month, bnt instantly 

 ejected them. 



The fry began to hatch out the day I got the nest ; three 

 ova hatched while under examination with the microscope. First 

 I saw distinctly the entire fish curled up in the shell of the 

 ovum ; a convulsive movement, and the tail protruded, and, by 

 a continuance of these convulsions, the entire fish freed itself 

 from the crust of the ovum in about twenty-five minutes after 

 the crust was first ruptured ; in some instances the head and tail 

 protruded simultaneously, in which case the crust of the ovum 

 remained round the fry like an awkward belt, which was not 

 got rid of uuder forty-eight hours. 



The newly-hatched fry is a quarter of an inch long, and is 

 furnished with a transparent membrane, like the fry of salmon 

 and trout. This membrane commences where the anterior dorsal 

 fin in the adult fish is seen, and continues unbroken till it 

 reaches a short way over the umbilical vesicle, where it ter- 

 minates. Inside this membrane, forming the outline of the fish 

 itself, a very fine dark brown line extends all round the fish, 

 and inside this a faint double streak of a pale orange colour. 

 These orange lines are blood-vessels, and, with a high power, 

 the blood-discs can be clearly seen running from and to the 

 heart, which is situated just under the lower jaw, its colour light 

 red, its beat rapid, the mouth of the fish opening with every 

 pulsation of the heart ; the eyes as well as the head are large, 

 the latter covered with several irregular dark brown spots. On 

 the day after hatching, the fish assumes much more colour, 

 losing its transparency, so that the flow of blood in the body 

 is not so clearly seen; but in the umbilical vesicle, which is 

 becoming rapidly absorbed, the flow of blood in its numerous 



els is very visible. The incessant motion of the pectoral 

 fins suggests the fluttering of a phantom, they are so transpa- 

 rent. 



( )n the third day after hatching, the fry is much more 

 covered, especially on the head, with dark brown spots, having 

 deeply serrated edges ; some of these spots also appear on the 

 ambiHca] vesicle Through this colour the heart is no longer 

 visible, nor any blood-vessels, except those between the rays of 

 the pectoral fins, which ;i re losing their transparency, and. are 

 at times for a moment stationary. Tho eyes as well as the 

 head occasionally move, the mouth continually opens and shuts ; 



crater circle of the eye can be perceived through the micro- 

 scope. The fry now ate very active, often swimming to the sur- 

 face ofthe water, then sinking gradually to the bottom, when, 

 after a short pest, they dart rapidly about again. 



( >" the fourth, fifth, and sixthday after batching, my infant 



klebacks make little progress; the umbilical vesicle is gra- 



