( hi ) 



and had served to show the extreme relative variability of all 

 the parts. Accurate measurements of this variability were 

 much needed for large numbers of individuals belonging to 

 widely different species in as many diverse groups of the 

 Animal Kingdom as possible. By this means naturalists 

 would in the future be better able to realise the degree of 

 plasticity of different organisms. Such information, which 

 might well be supplied by entomologists for insects, would 

 be of great value as a contribution to the theory of Natural 

 and Sexual Selection. 



Mr. Poulton said he was much interested in the results of 

 Mr. Merrifield's experiments. He was extremely astonished 

 to learn that an insect parasite and a perfect, although much 

 dwarfed, imago had been bred from a Selenia pupa. At the 

 same time he remembered that Prof. Westwood had shown 

 him a dipterous parasite which had escaped from a cocoon of 

 Trichiosoma lucorum, and from which the hymenopterous 

 insect had also emerged. Mr. Poulton thought that Mr. 

 Merrifield's experiments offered a most favourable opportunity 

 for practically testing whether acquired characters can or 

 cannot be transmitted. It was well known that certain larval 

 organs were the morphological equivalents of the corresponding 

 pupal and imaginal structures. Thus Mr. Poulton had found 

 that when the six ocelli of a lepidopterous larva had been 

 destroyed, the compound eye was not developed in the pupa 

 or in the imago. If any one of the larval thoracic legs were 

 cut off, the corresponding leg would almost certainly be 

 absent in the two later stages. Among all previously recorded 

 cases there had been no instance in which the effects of 

 mutilation had been proved to be transmissible to offspring. 

 Prof. Weismann, of Freiburg, had lately given many reasons 

 for believing that the transmission of acquired characters 

 (such as mutilations) cannot take place. But, as Mr. Francis 

 Galton had said, in all such previous cases the injury had 

 been inflicted comparatively late in life (viz., in Mammalia, 

 never before the close of intrauterine development), and in 

 order to finally show that such effects are not transmitted 

 they should be produced as early as possible in the life of the 

 parent. Such facilities are offered by Lepidoptera, for their 



PKOG. KNT. SOC. LOND., V., 1887. I 



