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jecting the pupae to cold, and found that some specimens reared under 

 normal conditions from the eggs produced by the aberrant forms 

 exhibited the same aberrations, but in a lesser degree. Weismann 

 obtained similar results with the same species. E. Fischer obtained 

 parallel results with Arctia caja, a brightly coloured diurnal moth of 

 the family Bombyciclce. Pupae of this moth were exposed to a 

 temperature of 8° C, and some of the butterflies that emerged were 

 very dark-coloured aberrant forms. A pair of these dark aberrants 

 were mated, and the female produced eggs, and from these larvae and 

 pupae were reared at a normal temperature. The progeny was for 

 the most part normal, but some few individuals exhibited the dark 

 colour of the parents, though in a less degree. The simple con- 

 clusions to be drawn from the results of these experiments is that a 

 proportion of the germ-cells of the animals experimented upon were 

 affected by the abnormal temperatures, and that the reaction of the 

 germ-cells was of the same kind as the reaction of the somatic cells 

 and produced similar results. As everybody knows, Weismann, 

 while admitting that the germ-cells were affected, would not admit 

 the simple explanation, but gave another complicated and, in my 

 opinion, wholly unsupported explanation of the phenomena. 



In any case this series of experiments was on too small a scale, 

 and the separate experiments were not sufficiently carefully planned 

 to exclude the possibility of error. But no objection of this kind 

 can be urged against the careful and prolonged studies of Tower on 

 the evolution of chrysomelid beetles of the genus Leptinotarsa. 

 Leptinotarsa — better known, perhaps, by the name Doryphora — is the 

 potato-beetle, which has spread from a centre in North Mexico south- 

 wards into the Isthmus of Panama and northwards over a great part 

 of the United States. It is divisible into a large number of species, 

 some of which are dominant and widely ranging ; others are restricted 

 to very small localities. The specific characters relied upon are 

 chiefly referable to the coloration and colour patterns of the epi- 

 cranium, pronotum, elytra, and under side of the abdominal segments. 

 In some species the specific markings are very constant, in others, 

 particularly in the common and wide-ranging L. decemlineata, they 

 vary to an extreme degree. As the potato-beetle is easily reared and 

 maintained in captivity, and produces two broods every year, it is a 

 particularly favourable subject for experimental investigation. Tower's 

 experiments have extended over a period of eleven years, and he has 

 made a thorough study of the geographical distribution, dispersal, 

 habits, and natural history of the genus. The whole work appears 

 to have been carried out with the most scrupulous regard to scientific 

 accuracy, and the author is unusually cautious in drawing conclusions 

 and chary of offering hypothetical explanations of his results. I have 

 been greatly impressed by the large scale on which the experiments 

 have been conducted, by the methods used, by the care taken to 

 verify every result obtained, and by the great theoretical importance 

 of Tower's conclusions. I can do no more now than allude to some 

 of the most remarkable of them. 



After showing that there are good grounds for believing that 

 Zool. 4th ser. vol. XIV.. Septemher, 1910. 2 E 



