70 BERTRAM G. SMITH 



Studies of the sex ratio indicate a more or less perfect segrega- 

 tion of the sexes at certain seasons of the year. A dozen adults 

 captured in June on the breeding grounds, by an assistant, 

 proved to be all males. During the summer, search of the breed- 

 ing grounds results in the capture of a few females and a much 

 larger number of males; in localities unsuited for breeding one 

 is more likely to find females, and males are seldom found in 

 their immediate vicinity. Just before the breeding season one 

 is more likely to find females on the breeding grounds, but the 

 males are still considerably in excess, and there is apparently 

 a tendency for the sexes to occur in groups: within a restricted 

 area one may find only males, while within another area a short 

 distance away one may find only females. At the height of the 

 breeding season, both sexes are found on the breeding grounds in 

 more nearly equal numbers. 



For some days or weeks after the close of the breeding season 

 the male remains in possession of the nest; females have never 

 been found in nests containing eggs. At this time females have 

 been found in considerable numbers in localities unsuitable for 

 breeding, with no males in their immediate vicinity. 



The general results of the studies of the sex ratio and the dis- 

 tribution of the sexes indicate that the males abound in localities 

 suitable for breeding, throughout the year, and that they are less 

 numerous elsewhere; it is positively established that the males 

 alone are in possession of the nests after spawning takes place; 

 and it is probable that there is a more or less perfect segregation 

 of the females from the breeding grounds during a period extend- 

 ing from the close of the breeding season until the middle of the 

 following summer. 



In Necturus, segregation of the sexes at a certain season of the 

 year seems to be more complete than is ever the case with Crypto- 

 branchus allegheniensis. Eycleshymer ('06) says: 



In the autumn they are found in pairs or small groups. From this 

 fact and others to be recorded later it is inferred that this is the mating 



season During egg-laying [in the spring] the males 



are never found with the females, and Avhere they remain is unknown. 



