186 



RejJrodKction in Simocephalus vetulus 



as they develop. The yonng however do not grow between ecdyses to 

 any extent detectable by the micrometer. An actual determination of 

 the coefficient of correlation between size of young and number of eggs 

 for S. vetulus gave — "74 + '04. The value for S. exspinosus, worked out 

 in larger numbers, gave as an average — •48. The values were computed 

 for groups for individuals belonging to the same generation and all 

 giving birth to theii- young nearly at the same time, and refer to first 

 broods only. 



As these experiments were primarily directed to the inheritance of 

 certain dimensions of the young, I have a large number of measure- 

 ments available. Table II gives the mean length of the new-born young 



TABLE II. 



Mean Length of the New-Born Yowkj {in first Brooda only). 

 Unit of Measurement = 0'018 mm. 



Note. The column "Number of Individuals" gives the numbei; of youns measured 

 in each generation, not the total number of voung born. When any brood contained 

 less than ten individuals all of them were measured, but when there were more than ten, 

 only the first ten, taken at random. Thus the mean number of young per brood cannot 

 be obtained from this table by dividing the number of individuals in each generation 

 by the number of broods. 



