50 THE GOLDFISH AND ITS CULTURE. 



and the more attenuated part or tail. In the water these little organ- 

 isms can live but one or two minutes, but when taken from the fish 

 and placed in a bottle kept at a proper temperature, they may be 

 preserved alive for six days. This discovery was made by a Russian 

 fish culturist in 1856 and is very important to the artificial propagation 

 of fish as it enables the crossing of different species. 



The eggs when first spent in the water have the shape of a slightly 



1 ^ / pressed in rubber ball, and as soon as they 



\}^ ""^o^-^ come in contact with liquid, they expand and 



t V^ suck it in through a microscopically small 



^ vl) k^ hole. (See illustration.) The spermatic germs 



y-i^ „^ — "X""" of the male being preseiit in this liquid are thus 



-^'^>>-Tp_^^,j''\. introduced and fertilize the egg. 



^ ' ' A — Spermatic Corpuscle. B — Gerininative Disk. 



Fektilization of Fish Egg. C—NutHtive Yolk. 



The fecundation of the egg consists in the entry of the spermatic 

 corpuscles and the subsequent production of a subdivision of the 

 germinative disc, which phenomenon is called the process of "seg- 

 mentation " or "furrowing." This is followed by a series of successive 

 changes, of which the final result is the embryo, which, subsisting or 

 being nourished by the yolk, gradually develops into the perfect fish. 



The young fish when first hatched is supplied with a sac called 

 \ht yolk-b(jg, from which it derives its nourishment during the early 

 period of its independent existence. When this has been exhausted 

 it is then ready to seek other food and this it finds in various 

 niicroscopic organisms that exist in profuse abundance in the water. 

 As the fish grows larger and gains strength, other and coarser food is 

 sought and devoured. 



