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 885 when first spent in the water have the shape of a slightly 
pressed in rubber ball, and as soon as they 
come in contact with liquid, they expand and 
suck it in through a microscopically small 
hole. (See illustration.) Zhe spermatic germs 
Cc of the male being present in this liquid are thus 
introduced and fertilize the egg. 
A—Spermatic Corpuscle. B—Germinative Disk. 
FERTILIZATION OF FisH Eee. C—WNutritive 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- 
” This is followed by a series of successive 
mentation” or ‘‘ furrowing. 
changes, of which the final result is the edézyo, 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 
the yo/k-bag, 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 
microscopic 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. 
