40 



THE 



AQUARIUM 



^ 



it possible to practice the line-breeding 

 plan of the poultry fancier, this would 

 not be so essential. 



Animals, having the power of loco- 

 motion, and free to move about from 

 place to place mingling with their kind, 

 have not been provided with means to 

 prevent inbreeding. Movement, restrict- 

 ed only by the climatic and food re- 

 quirements of the species, renders the 

 liabihty of consanguinity very slight. 

 Plants, however, have developed various 

 means to insure cross-fertilization. Many 

 species bear the male and female flowers 

 on separate individuals, or, when a 

 species produces flowers of both sexes, 

 or hermaphrodite (combination) flowers 

 on the same plant, the organs of the 

 sexes do not mature simultaneously, 

 thus making fertiUzation by another 

 plant necessary. The pollen, or male 

 element, is carried from flower to flower 

 by the wind or insects. 



Nature frowns with equal vehemence 

 upon inter-breeding of divergent species, 

 or hybridizing. The result is usually loss 

 of vigor, degeneracy and sterihty. More 

 commonly, even though the individuals 

 may be of closely related families, the 

 attempt is productive of no result what- 

 ever. Anatomically, the animals may be 

 very much ahke, yet the spermiatozoon 

 of the male is unable to effect the ovum 

 of the female. There are, however, in- 

 stances where the offspring, while sterile, 

 and thus unable to reproduce their kind, 

 are yet vigorous. The mule may be cited 

 as an example. A hybrid has been se- 

 cured by crossing the American bison 

 (buffalo) with the domestic cattle that 

 is said t6 be very vigorous. Exceptions, 

 of course, may be found to any rule, 

 but when we oppose Nature, we have 

 forces arrayed against us, the workings 

 of which we do not comprehend. Far 



better that we enlist the help of the 

 Laws of Nature than to controvert her 

 power. 



Goldfish breeders, working as they do 

 with the very concentrated product of 

 selective inbreeding, should make every 

 effort to out-breed without losing the 

 desirable characteristics they aim to re- 

 tain in their stock with increased de- 

 velopment. The writer is familiar with 

 the methods and stock of some of the 

 breeders of the best goldfish in America, 

 and knows well that inbreeding is un- 

 intentionally practiced to the detriment 

 of their strain. Father and daughter are 

 being bred together. Splendid develop- 

 ment of fins is being secured, but on 

 fish of extremely low vitality and short 

 lives. With the usual methods of breed- 

 ing, it is almost an impossibility not to 

 inbreed. The fry are gradually assorted 

 according to size without regard to 

 parentage. Every breeder, sooner or 

 later, by judicious selection of males and 

 females, hits upon a combination that 

 produces a number of fry of excellent 

 form. With his desire for perfection, it 

 is natural, that when this same fry has 

 grown to maturity, relationship not be- 

 ing positively known, he will mate 

 brother and sister together. The result 

 is very apt to be weaklings. My opinions 

 may be disputed and considered mere 

 theory, but 1 feel that it will be hard to 

 adduce facts to offset them, as pedigree 

 breeding is scarcely possible with gold- 

 fish. The columns of the magazine are 

 open for a discussion of this subject. 



The Diatomacea as Food for 

 Fish Fry 



By W. A. POVSER, Hammond, Ind. 



Mr. Smith, in his interesting article on 

 Plankton and Nepton in the June issue, 

 has indicated a field which is not only 



