No. 3567 LABIDOCERA JOLLAE GROUP—FLEMINGER 35 
to recurrent environmental fluctuations (see Ford, 1964, for examples 
and discussion). Evidence that the male morphs of diandra have 
a genetic origin is presented below. 
Polymorphism of sexual structures in marine Calanoida is not a 
familiar phenomenon. One case presented in an unpublished thesis 
by Fleminger (1956) involves Pontella meadii, a surface species in- 
habiting transitional warm-temperate coastal waters of the eastern 
United States. In this area the offshore climate provides a year- 
round warming influence that is overcome to varying degrees in 
winter by the continental climate. The resulting seasonal changes 
are probably not too dissimilar to the variable conditions experienced 
by populations of ZL. diandra in the northern segment of its range and 
in areas of seasonal upwelling. Two forms of the adult male of P. 
meadw are known, one described by Wheeler (1900) and the other 
described as P. pennata by Wilson (1932). Regarding the female, 
Wheeler worked only with stage V copepodites and apparently 
assumed they were adult. Wilson described the adult female as 
pennata along with the larger sized male morph. More recently, 
Haq (1960, 1965) reported finding genetic polymorphism in laboratory- 
bred Huterpina acutifrons (Harpacticoida). Two morphologically dif- 
ferent kinds of adult male are described. Johnson (1964) found two 
kinds of male of Pseudodiaptomus wrightt which differ in several 
structural features including the size of the fifth pair of legs; however, 
only three examples of the morph with the larger fifth legs were 
observed in the hundreds of male specimens examined. In L. diandra 
and P. meadii both morphs are relatively common and occur through- 
out the range of the species. 
DEVIATION IN THE SEX RATIO IN LABIDOCERA DIANDRA 
Comparison of the relative abundance of males and females in 
diandra revealed a conspicuous deviation in the adult stage from an 
expected 1: 1 ratio (table 9). Abundance estimates were obtained by 
tabulating the species in the entire sample, excepting tow F-5; for 
the latter a large subsample was counted. 
Using pooled data stage V males and females do not differ signifi- 
cantly from a 1:1 ratio (x?=7.58, p=0.025—0.020). In the adult 
stage, however, males exceed females by 1.0:0.69, the deviation from 
1:1 being highly significant (x’?=157.5, p=<.0.001). These relation- 
ships apply to summed data but not necessarily to values obtained 
from any single collection. 
Despite extensive variation in the numbers of adults, males exceeded 
females appreciably in six of the seven large collections of the species. 
In the seventh (El Golfo station 24), males are too rare for the sample 
to be regarded as representative. Considerable variation in the rel- 
