2o6 Experimental Zoology 



determined, but Crampton found no evidence that the death 

 could be assigned to such causes. 



Only i8i perfect moths (97 males, 84 females) emerged; 75 

 were imperfect to a slight degree, 38 were malformed, and 16 

 failed to metamorphose at all. It will be seen that only 16.6 

 per cent of the individuals that pupated became perfect adults. 



Measurements of the pupae show that the survivors are longer, 

 narrower, and deeper than the ehminated pupae. It also appears 

 that survival does not necessarily or invariably accom.pany a 

 condition of lower variabihty, although such a relation is gen- 

 erally observed. Crampton's general conclusion is that the 

 elimination is based on the general and total efficiency of the 

 individual, and "this is determined by the proper coordination 

 of functional and structural elements. The actual basis for 

 elimination is, in a word, * correlation.' If this correlation is 

 sHght, the individual ranks as unfit ; if it is higher, the individual 

 is fit and more likely to survive." Whether the correlation itself 

 determines the outcome, as Crampton appears to mean, or 

 whether the lack of correlation is due to some deeper-lying im- 

 perfection, such, for example, as the presence of disease in the 

 caterpillar which determines both the lack of correlation and the 

 failure to develop, cannot be stated. If the latter is the case, the 

 lack of correlation is only an index of a diseased or imperfect 

 organization, and therefore not in itself responsible for the 

 elimination. Crampton's idea, however, is that the imperfect 

 correlation is due to formative factors in the insects themselves 

 which leads directly to their death, and not to elimination due to 

 external conditions. 



Variation and Parthenogenesis 



The problems of variation and of inheritance have generally 

 been studied in animals that reproduce sexually. In only a few 

 parthenogenetic forms, namely, in some insects, in aphids 

 and in the honey bee, and in the crustacean, Daphnia, 

 has the problem of variation been examined. Weismann ad- 

 vanced the idea that the purpose of sexual reproduction is to 



