666 



SCIENCE. 



[N. S. Vol. XX. No. 516. 



have escaped an early deatli from tubercu- 

 losis, what procedure is indicated? 



We can not always take refuge from the 

 consequences of inaction under the plea of 

 ignorance. There are few, if any, instances 

 where public hygiene is utilizing to the 

 full the knowledge that it might possess. 

 Some responsibility rests upon those who 

 are prosecuting bacteriological studies to 

 see that the bearings of their investigations 

 are not overlooked or neglected by those 

 who are constituted the guardians of the 

 public health. There is here no question of 

 the sordid self-interest or commercial ex- 

 ploitation sometimes miscalled ' practical 

 application.' In the long run the saving of 

 life may play into the hands of the idealist. 

 If John Keats had not died of consumption 

 at the age of twenty-five the modern world 

 would be a different place for many per- 

 sons. It is not possible to estimate the loss 

 to literature, science and art since the dawn 

 of intellectual life which must be laid at 

 the door of the infectious diseases. The re- 

 lations of bacteriology to public hygiene, if 

 properly appreciated and cultivated, will 

 lead to an improvement in the conditions of 

 life which will enhance both the ideal and 

 material welfare of the race and will give 

 greater assurance that each man shall com- 

 plete his span of life and be able to do the 

 work that is in him. 



Edwin Oakes Jordan. 



Univeksitt op Chicago. 



EVOLUTION OF WEEVIL-RESISTANCE IN 

 COTTON. 



The complexity of biological problems 

 finds another excellent illustration in the 

 evolutionary history of the relations be- 

 tween the cotton plant and the so-called 

 Mexican boll-weevil. The present indica- 

 tions are that both the cotton and the 

 weevil originated in Central America. The 

 parasitism of the beetle is certainly very 

 ancient, if, as seems to be the case, it has 



no other breeding-place than the young 

 buds and fruits of the cotton plant. Of the 

 severity of the parasitism there is ample 

 evidence in Texas, the weevils being able 

 to totally destroy the crop when the cli- 

 matic conditions admit of their normal 

 increase. 



It was to have been expected, therefore, 

 that in humid tropical localities where all 

 seasons of the year are alike favorable the 

 cotton would have been exterminated long 

 since, or at least that its cultivation as a 

 field crop would be utterly impracticable 

 unless there were means of protection 

 against the ravages of the insect. A defi- 

 nite intimation of the existence of protect- 

 ive adaptations was incidentally gained in 

 eastern Guatemala in 1902 when no weevils 

 were found in a field of the dwarf cotton 

 cultivated by the Indians, although they 

 were extremely abundant on a perennial 

 'tree' cotton a short distance away. The 

 opportunity of making a detailed study of 

 the subject during the second quarter of 

 the present year has revealed an interesting 

 series of protective adaptations resulting 

 from the long evolutionary struggle for 

 existence between the cotton and the weevil. 



Reference has been made in another 

 place* to the extensive system of extra- 

 floral nectaries by which the cotton of 

 eastern Guatemala has secured the active 

 cooperation of the kelep or weevil-eating 

 ant, but the Central American cottons and 

 the Indians who have been cultivating them 

 for thousands of years have developed 

 many other expedients of structure, habits 

 and culture which are of more or less as- 

 sistance in resisting or avoiding the weevil. 



The large leafy involucre of the cotton 

 may have been at first a protective adapta- 

 tion, though the weevils later learned to 

 enter it easily. In some of the Guatemalan 

 sorts the bracts are grown together at the 

 base as though the evolution of a closed 



* Report No. 78, U. S. Dept. Agric, p. 4, 1904. 



