14 MINNOWS GAMBUSIA AFFINIS AND CYPRINODON VARIEGATUS. 



some of them before they reached the wire screen. Several dissec- 

 tions made on April 17 showed that the ovary of a large female con- 

 tained about 140 well-developed eggs, fiiUy half of which seemed to be 

 of one size and generally nearly mature. To acquire more data on this 

 pomt, artificial spawning was tried with a number of females. The 

 process of stripping, however, involves more handling than the 

 species endures, and none of the females lived to produce more than 

 two sets of eggs. 



Females of this species may be found in spawning condition as 

 early as the middle of March and as late as October 1. "VMiether the 

 early spawners continue to spawn as late as October or if these late 

 spawners are those that began spawning later in the season is not 

 known. Our aquarium specimen, which was an early spawner, had, 

 under abnormal conditions, spawned out by August 16. 



Tig. i.— Cyprinodonvariegatus. Variegated minnow. Young. 



The feggs of this species are somewhat heavier than salt water. 

 They are spherical in form and about 1 mm. in diameter. Incubation 

 at laboratory temperature occupies five to six days. The newly 

 hatched young are 4 mm. in length (Kmitz, 1916, p. 414). They 

 grow rapidly and by the beginning of August some of the largest are 

 as much as 32 mm. in length. Up to this age the sexes are colored 

 alike and resemble the adult female, but at about this time the young 

 male assumes the adult markings and hereafter it can with difficulty 

 be distinguished from an adult male. 



My observations show that this is a very prolific species, and its 

 fecundity may be held to explain in a measure its great abundance. 

 It is said to be of some value as an eradicator of mosquito larvae, but 

 its greatest economic importance probably lies in the food it furnishes 

 for larger fishes. 



In this connection it may be mentioned that observations in the 

 field and dissections made at various times during two seasons strongly 



