EVOLUTION 1003 



changes. Though functional rather than structural, it is an acquired 

 character in the Lamarckian sense, changing the physiological 

 reaction of the entire organism to an external stimulus. And, as the 

 result of the work of Hanson and Heys is to show no trace of the 

 handing on of the acquired resistance, no support for the Lamarckian 

 hypothesis is forthcoming along this line. 



Alcoholic Degeneration in Rats. — As there has been some 

 discrepancy in the results of treating animals for successive genera- 

 tions with alcohol fumes, we may sum up the present state of the 

 case: (i) Stockard and Papanicolaou found that the untreated 

 offspring of treated guinea-pigs were defective in fertility and in the 

 quality of the offspring they produced. This was attributed to a 

 deterioration of the germ-cells. (2) But Raymond Pearl got the 

 opposite result with his hens, finding that in eight points the off- 

 spring of treated parents, either one or both, were superior. This was 

 attributed to an elimination of the weaker germ-cells. (3) Stockard 

 accepted Pearl's idea of the selective agency of alcohol, but retained 

 a belief in general deterioration of germ-cells. The weakest were, he 

 supposed, entirely eliminated, but the survivors were also weak, 

 and gave rise to defective offspring, which often died before birth 

 or soon after. Those offspring which lived to reproduce gave birth 

 to defective offspring because "weak cells give rise to other weak 

 cells". (4) Hanson holds that alcohol acts as a selective agent only, 

 and produces no new, heritable variations. In their recent paper, 

 Hanson and Heys write: "It seems evident that none of the experi- 

 ments with alcohol thus far presented gives any indication that 

 alcohol has produced a specific alteration of germ plasm, as would 

 be demanded had an acquired character been transmitted." (5) It 

 appears to us, however, that Stockard's result indicates general 

 deterioration of the germ-cells as well as the elimination of the 

 weakest. Though this may not involve "a specific alteration of the 

 germ plasm", it may imply a weakening of the whole stock. A 

 weakening of the germ-cells may operate in a very deteriorative way, 

 not only by sapping developmental vigour, but by disturbing the 

 regulative processes on which normality depends. The last word has 

 not been said. We are all tired of alcoholised rats, yet we must hear 

 about them again. 



Melanism in Moths, and Its Causes. — ^The most noteworthy 

 evidence so far for the evolutionary influence of environmental 

 conditions upon insects are the recent studies of Harrison and 

 Garrett on the development and rapid progress of melanism, in 

 species after species of British moths. This change is confined to 

 the industrialised districts, and is also being reported from those of 

 Germany and the United States. Smoke and light deficiency, 

 dampness, etc., having proved inadequate as explanations, even 

 when supplemented by natural selection, the suggestion next arose 



