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American Ln)e-Bearing Tooth-Carps 



DR. E. BADE 



The last few years have witnessed a 

 tremendous growth of aquarium societies 

 and an augmented interest in keeping and 

 raising fishes in the balanced aquarium 

 at home. The little live-bearing tooth- 

 carps of America have undoubtedly been 

 among the main factors contributing to 

 the advancement. They are easy to keep 

 and readily multiply in captivity. 



The male is, as a rule, smaller than the 

 female, and has its anal fin modified into 

 a long intromittent organ. The pos- 

 terior part of its body has more verte- 

 bra; than the female. Several of these 

 are modified to form a support for the 

 mass of muscles involved in the compli- 

 cated movements of the anal fin during 

 copulation, the muscles being attached 

 directly to the vertebral column by tough 

 ligaments. The shape of the modified 

 anal fin varies in the different species, 

 especially the clasp-like tip, which is 

 probably used for holding or grasping 

 the small projection (papilla urogeni- 

 talis) just behind the anus of the female. 

 On the underside of the bone-like ray 

 of the anal fin is a small canal for the 

 sperm. When fertilization is carried on 

 the intromittent organ moves forward 

 with a motion not unlike that of a clasp- 

 knife being opened. Through this motion 

 the canal, which at first lay downward, 

 now faces up. This is characteristic of 

 Cnesterodon decemmaculatus and Glari- 

 dichthys januarius. In what respect some 

 of the other species may differ is at pres- 

 ent unknown. Fitsroyia and Anableps 

 have tube-like intromittent organs, and 

 the sexes are developed into rights and 



1 



lefts ; a "right" male consorts only with a 

 "left" female, and vice versa. Other 

 tooth-carps cannot be classified in this 

 manner. 



The eggs are fertilized internally and 

 remain in the ovary during incubation. 

 After one fertilization the female expells 



Poecilia vivipara 



a number of broods, even though weeks 

 and months may intervene, for only 

 those eggs which are fully mature are 

 fertilized. A receptaculum seminus for 

 storing the sperm is formed by numerous 

 unsymmetrical folds in the lining of the 

 oviduct. Here the spermatozoa are found 

 in great numbers, even after the expul- 

 sion of a brood. This is used to fertilize 

 eggs subsequently matured as they come 

 forward. The female constantly endeav- 

 ors to escape copulation until all the 

 stored sperm has been used. 



The period of incubation lasts from 

 four to six weeks, although it may be 

 longer if the water in the aquarium is too 

 cool. The young are expelled when fully 

 developed, the number in a brood vary- 

 ing considerably. Premature births are 



