424 



THE POPULAR SCIENCE MONTHLY. 



same ancestor was once surprised by hear- 

 ing some one speak of his father's sleigh as 

 being green on the outside and red on the 

 inside, for it had always appeared to him 

 to be of the same color on both sides. He 

 was also heard to remark that he could see 

 no change in the color of the maple-leaves, 

 which, as we all know, turn from their sum- 

 mer green to red, and then to brown. This 

 form of color-blindness is particularly in- 

 convenient to pei'sons who wish to pick 

 cherries or stra\i'berries, for they have only 

 the forms to guide them, without any help 

 from the color. One of the brothers of the 

 grandfather and two of his first-cousins had 

 the same defect, and a nephew in the next 

 generation. The youth spoken of in the 

 beginning of this notice is the first in the 

 present generation who has manifested it. 

 Generally the affection appears to have been 

 transmitted through the female line of the 

 family, but to sons, and not to daughters. 

 Exceptions to this rule are noticed in the 

 case of a ccreat-uncle of the vouth's mother, 

 who inherited it from his father and trans- 

 mitted it to his four sons ; and of a fe- 

 male relative, through whom it was trans- 

 mitted to two daughters. By means of 

 the instances related, the course of the af- 

 fection is traced through five generations. 



Why Prairies are Treeless, Mr. Thomas 

 Meehan believes that we have nearly reached 

 the solution of the question of the cause of 

 the absence of trees from the prairies. It 

 is not climatic, for timber-belts flourish in 

 all the prairie regions. It is not in condi- 

 tions of soil, for the prairie soil is the most 

 favorable to the germination of seeds, of 

 trees as well as of other plants, and arti- 

 ficial plantations are remarkably successful 

 wherever they are made. The real cause is 

 probably to be found in the annual fires 

 which have swept over the prairies from 

 time immemorial, killing the young trees 

 before they can grow large enough to resist 

 the heat. The seeds of the annual plants 

 of the prairie vegetation, maturing every 

 year, are shed and find protection before 

 the fires come; the young trees, on the, 

 other hand, bear no seed, and can leave 

 no resource for a succession after they are 

 burned. This theory is supported by the 

 fact that an abundant growth of trees has 



set in wherever the fires have been stopped. 

 The fires were made by the aborigines for 

 centuries before the white men came, pos- 

 sibly for the express purpose, Mr. Meehan 

 suggests, of preventing the growth of trees 

 and preserving the buffalo-pastures. The 

 question remains how the prairies first came 

 to be naked. They probably formed the 

 bottoms of the lakes and marshes that were 

 left after the retreat of the glaciers, and 

 continued wet after the highlands were cov- 

 ered with trees. Man followed the glaciers 

 so closely that he anticipated the trees on 

 these spots, and, having learned already in 

 southei^n latitudes the value of burnings, 

 began them before the trees gained a foot- 

 hold. 



Darwin's Views on Vivisection. The 



following is Mr. Darwin's reply to a letter 

 from Professor Holmgren, of Upsala, re- 

 questing his views on the right to make 

 experiments on living animals in the interest 

 of science: 



Down, Beckenham, April 14, 1881. 

 Deak Sir : In answer to your courteous let- 

 ter of April 7tli, I have no objection to express 

 my opinion with respect to the right of experi- 

 menting on living animals. I use this latter 

 expression as more correct and comprehensive 

 than that of vivisection. You are at liberty to 

 make any use of this letter which you may think 

 fit, but if published I should wish the whole to 

 appear. I have all my life been a strong advo- 

 cate for humanity to animals, and have done 

 what I could in my writings to enforce this 

 duty. Several years ago, when the agitation 

 against physiologists commenced in England, it 

 was asserted that inhumanity was here prac- 

 ticed, and useless suffL-ring caused to animals; 

 and I was led to think that it might be advisable 

 to have an act of Parliament on the subject. I 

 then took an active part in trying to get a bill 

 passed, such as would have removed all just 

 cause of complaint, and at the same time have 

 left physiologists free to pursue their researches 

 a bill very diflFerent from the act which has 

 since been passed. It is right to add that the 

 investigation of the matter by a RojmI Commis- 

 sion proved that the accusations made ngainst 

 our English physiologists were false. From all 

 that I have heard, liovvever, I fear that in some 

 parts of Europe little regard is paid to the suf- 

 ferings of animals, and if Ibis be the case I 

 should be glad to hear of legislation against in- 

 humanity in any such country. On the other 

 hand, I know that physiology can not possibly 

 progress except by means of experiments on 

 living animals, and I feel the deepest conviction 

 that he who retards the progress of physiology 

 commits a crime against mankind. Any one 



