50 



THE AQL^ARIUM, JULY, 1893. 



the female, all the while ejecting his 

 sperm over the eggs. 



The eggs 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 the liquid they expand 

 and suck it in through a microscojuc- 

 ally-small hole. 



The spermatic germs of the male be- 

 ing present in this liquid are thus intro- 

 duced and fertilize the egg. 



The fecundation of the egg consists 

 in the entry of the spermatic corpuscles 

 and the subse- 

 quent produc- 

 A tion of a subdi- 

 f /^ ^C!* -B ^'ision of the 



'"*! \ZJ n- g e r m i n a t i V e 



/A yT^" " disc, which phe- 



^^'-.j—^^^X nomenon is call- 



' ) ' ed the process 



Fertilization OF Fish Egg. f '^' apo-monfi 

 Enlarged. ^'^ segmeuca- 



A Spermatic corpuscle. tion " Or "fur- 



B. Germinative disk. 



C. Nutritive yolk. rowillg." Tllis 



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 de- 

 velops into the perfect fish. 



The young fish when first hatched is 

 supplied with a sac called the yolk-bag, 

 from which it derives its nourishment 

 during the early period of its independ- 

 ent existence. When this has been 

 exhausted it is then ready to seek other 

 food, and this it finds in various micro- 

 scopic 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. 



Note. — Although fish spawn a great 

 number of eggs, comparatively few of 

 them are destined to develop into per- 

 fectly mature fish. Nevertheless they 

 cannot be said to be totally wasted, as 

 short-sighted enthusiasts suppose, ^' for 



nature doeth all things well." There 

 are many denizens of the water whose 

 sole duty it is to devour these super- 

 abundant eggs, thus preventing what 

 would otherwise be a destructive over- 

 production. Insects and Crustacea feed 

 upon them, and are in turn consumed 

 by fish that in their turn serve as food 

 for larger ones or titillate the palate of 

 omnivorous man. 



THE TEOUT-LIKE FISHES. 



Salmnnidae. 



The several members of this family 

 of fish are highly esteemed for the 

 table. They are found at any elevation, 

 from the sea level to the snow limit. 

 They vary greatly in several particulars, 

 according to the locality in which they 

 thrive, the quality of food upon which 

 they subsist and the differences incident 

 upon age and sex. For these reasons: 

 The family has been subdivided into a 

 great number of species, which sub- 

 division is, at best, but nominal. The 

 dominant characteristic by which any 

 species may be distinguished and which 

 is common to all, is an adipose, or fat fin, 

 back of a short dorsal fin. They may 

 be further characterized by the naked 

 head, a body covered with comparatively 

 very small scales of uniform size, both 

 jaws being armed with sharp teeth, 

 the belly round and the air bladder 

 large and simple. Another distinction 

 is conspicuous by its absence, namely, 

 barbies. There are about 160 recog- 

 nized species of this family, from which 

 we select the following ones as the lead- 

 ing representatives of their type. 



THE SALMON. 



Der Lacks. Salmo Salar. Le Saumon. 



The body of this fish is long, the head 

 sharp and, compared with the size of 



