EVOLUTION 1013 



to the transmission of parentally acquired characteristics, to which 

 Lamarck attached a much greater importance, he explicitly accepted 

 the possibility. To Lamarck the raw materials of evolution seemed 

 in the main "modifications" (exogenous) ; to Darwin the raw materials 

 of evolution seemed in the main "variations", arising, he knew not 

 how, from within. 



Everyone must welcome recent work bearing on the transmissi- 

 bility of modifications, and such convinced statements of the affirma- 

 tive position as Prof. MacBride has given us. But there is great 

 need for caution, and it may be of interest to refer to two or three 

 pieces of evidence, which show the difficulty of getting a clear-cut 

 result, admitting of the Lamarckian interpretation and of no other. 



Return to Stockard's thirteen years of experiments with guinea- 

 pigs which he treated with fumes of alcohol. Over 5,000 animals 

 were used, and several were treated for as long as six years. 

 Some of the treated animals lived for over seven years, probably 

 the longest life span recorded for guinea-pigs. The fumes did not 

 injure or noticeably modify the structure or behaviour of the 

 treated animals. "But while the parents lived long and well, their 

 descendants showed a high early mortality and were structurally 

 defective in many cases." Is this evidence of the transmission of 

 acquired characters? This is not Prof. Stockard's view, for he 

 thinks that the alcoholic poison saturating through the body of the 

 treated parent affected the germ cells prejudicially, so that they 

 subsequently gave rise to low grade or arrested offspring. The weak 

 and defective offspring and later descendants of the alcoholic 

 guinea-pigs never showed any "new character" or any exact condi- 

 tion that was acquired by the parents or progenitors as the result 

 of the inhaling treatment. This is only one out of several similar 

 experiments; it serves to illustrate the need for critical caution. 

 Others, moreover, have failed to confirm his lesults. 



Doctors Bentley and Griffith in Philadelphia rotated rats at 

 speeds of 60-120 revolutions per minute and kept it up for 2-18 

 months. The rats fed and bred, played and slept in their revolving 

 cages. When they were liberated, some fell into a decline and died, 

 others exhibited, sooner or later, marked disturbances in their 

 locomotion and eye movements. Some of them were paired with 

 normal rats, and the offspring showed a high proportion of "dis- 

 equilibrated" individuals. This looks very like the handing on of a 

 specific disturbance, and this may he the correct interpretation. But 

 Dr. Detlefsen has put his finger on a possible fallacy. The whirling 

 may have set up inflammatory processes in the inner ear; there 

 were often discharges from the ears of the rotated rats; and it may 

 be that there is an associated pathogenic microbe which might pass, 

 by contact, for instance, from parent to offspring. Dr. Detlefsen 

 studied twenty cases of "spontaneous" ear inflammation among 



