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Ten stuttering and 10 nonstuttering subjects performed self-paced rhythmic tasks with the finger and jaw and were asked to repeat “ah.” The tasks were performed at three rates: “comfortable” rate; and “slightly higher” and “slightly lower” than comfortable, but still in the comfortable range. The stutterers performed each of the three tasks more slowly than the nonstutterers and were less variable than nonstutterers. The reduced rates and more constrained variability of the stutterers were interpreted as manifestations of less flexible systems, which may be more susceptible to breakdown.

Maternal injections of adrenalin and saline 3 to 4 days after mating, as compared to injections during the second and third trimesters, resulted in significantly fewer litters in an inbred strain of mice (A/J). However, no such effect was noted in the C57BL/6J strain, suggesting the presence of a genotype-environment interaction. The possibility that the blocking of pregnancy in the A/J strain results from a failure of implantation is discussed.

Heritability estimates for corneal power were found to be high and similar for two populations which differed in their incidence of esotropia. This similarity suggest (1) that genetic differences for corneal power do not contribute to the difference in heritability for spherical refractive error reported for these populations and (2) that this character is not a critical variable contributing to the pathophysiology of esotropia. Heritability estimates for corneal astigmatism were, in most cases, rather low. The pattern of population and sex differences among heritability estimates was consistent with those previously reported for cylindrical refractive error. These population differences in heritability suggest that they contribute to population differences found for cylindrical refractive error.

In segregating F(2), F(3), and F(4) generations, albino mice had lower activity and higher defecation scores than pigmented animals when tested in a brightly lighted open field. These differences persisted when members of an F(5) generation were tested under white light, but largely disappeared under red light. Thus it was concluded that there is a major gene effect on the quantitative traits of open-field activity and defecation which is mediated by the visual system and that albino mice are more photophobic than pigmented mice under conditions of bright illumination.

Ovaries from donors of each of two inbred strains (BALB/cJ and C57BL/6J) were transplanted into F1 hybrid recipients. By appropriate matings it was thus possible to obtain inbred offspring carried by either hybrid or inbred mothers. Differences in the maternal environment were found to account for a relatively small proportion of the total variance in open-field behavior, but accounted for a relatively large proportion of the variance in body weight.

Open-field activity and defecation scores on each of two successive days were obtained on 637 F2 and S41 F3 Ss and subjected to genetic analysis, Heritabilities of second-day activity and defecation scores were found to be lower than those of first day scores. Genetic and phenotypic correlations among the single-day behaviors were also estimated. From these results it was concluded that activity on Days 1 and 2 and defecation on Day 2 are influenced by many of the same genes and that high open-field activity on Days 1 and 2 are both indices of low emotional reactivity.