MINNOWS GAMBUSIA AFFINIS AND CYPRINODON VARIEGATUS. 7 



second brood, July 2; third brood, July 18; fourth brood, August 9; 

 fifth brood, August 30; and sixth brood, October 5. It is probable 

 that some females produce an even greater number of broods during 

 a single season, for it was noted that several females in the aquaria 

 gave birth to yomig diu-ing a period of two to three weeks after the 

 individual just cited had concluded for the season; some also began 

 bearing at an earlier date than this one. Presumably the effect of 

 aquarium life would be to reduce rather than to increase the number 

 of broods..' As the temperature of the water seems to determine 

 the time of beginning of the spawnmg season, it probably influences, 

 to some extent at least, the rapidity with which the later broods are 

 developed. The aquarium in which the above-mentioned female 

 lived was kept in the writer's office, where it was protected from the 

 direct rays of the sun. The water in it, therefore, never reached 

 the luke-warm temperature of that usually occupied by these fish 

 in nature, and for that reason it may be supposed to have exercised 

 a retarding influence upon the development of the successive broods. 



The number of young comprising a single brood appears to bear a 

 direct relation to the size of the female. If the female is small, a 

 small brood results. If the female is large, a more numerous brood 

 may bo expected. That the earher broods are larger than the later 

 ones, as suggested by Dr. H. M. Smitli (1912, p. 224), could not be 

 verified. A large number of dissections of specimens obtained at 

 various times during the season revealed no differences that would 

 substantiate that suggestion. In the same paper Dr. Smith states 

 that the average number of embryos contained in the ovary of a 

 limited number of fish dissected or observed by him at the aquarium 

 of the Bureau of Fisheries in Washington was 100. Dealing with 

 specimens from the Beaufort region, the largest number found by the 

 present writer in any single ovary was 63, and the average among the 

 largest females obtained did not exceed 40. Dr. Albert Kuntz 

 (1914, p. 183), working with fishes from the Beaufort region, found 

 76 to be the maximum number produced by a single female. The 

 fish examined by Dr. Smith were from the Potomac River and 

 measured from 45 to 50 mm, in length. They were, therefore, not 

 so large as some of the specimens under observation at Beaufort, 

 the largest of which are 64 mm. in length. The number of broods 

 of one season produced by a single female in a more northern lati- 

 tude are probably fewer in nmnber, owing to the shorter period of 

 warm weather; but since the observations of Dr. Smith suggest 

 that the broods may be larger, it is possible that the number of 

 young produced during a single season is not materially smaller in 

 the higher latitude. 



It is an interesting fact that females separated from males even 

 before the first spring brood is born contiiiuc to produce young 



