Decembek 16, 1921] 



SCIENCE 



597 



6. CONDITIONS INFLUENCING THE HATCHING OF 

 HOOKWORM EGGS 



Hookworm eggs hatch as readily in ashes 

 as in soil. Hookworm eggs in feces buried 

 to a depth of from 1/2 of an inch to 2 inches 

 hatch and the larvae develop in numbers, there 

 being only a slight retardation in develop- 

 ment. Wlien eggs were buried from 4 to 

 5 1/2 inches in a clay loam soil, only a few 

 larvae were able to develop. The invasion of 

 the stools by numbers of fly larvaj was found 

 to be detrimental to the development of hook- 

 worm larvse to the infective stage. 



7. THE FINDING OF UNSHEATHED HOOKWORM 



LARViE IN THE SOIL 



The finding, both in field and laboratory 

 studies, of a large percentage of mature hook- 

 worm larvse without their protective sheaths, 

 led to the conclusion that a large proportion 

 of such larvffi in the soil complete their second 

 larval moult and continue to live in the un- 

 sheathed condition. 



8. VERTICAL 3IIGRATI0NS OF INFECTIVE HOOK- 



WORM LARV^ 



It was found that under certain condi- 

 tions mature hookworm larvae when buried 

 to a depth as great as 5 1/2 inches can 

 migrate to the surface. In such a migration 

 the larvse used up most of their reserve food 

 supply, so that after reaching the surface 

 they were relatively inactive and the cells 

 of the intestine had become almost trans- 

 parent. 



9. HORIZONTAL MIGRATIONS OF INFECTIVE HOOK- 

 WORM LARV^ 



From laboratory experiments and field ob- 

 servations it was found that mature hook- 

 worm larvte do not migrate actively from 

 their place of development, although they 

 may be carried to considerable distances by 

 the action of water or on the feet of man. 

 These observations showed that the present 

 idea that tlie soil of considerable areas can 

 be infested by the migrations of the larvse 

 from limited centers is untenable. 



10. LENGTH OF LIFE OF INFECTIVE HOOKWORM 

 LARVjE in THE SOIL 



Under the conditions in Trinidad the 

 length of life of infective hookworm larvse 

 in the soil is short, almost never exceeding 

 six or seven weeks. In an area of a cane 

 field where there was intense soil infestation 

 there was a reduction of over 90 per cent, 

 in the numbers of larvse in about three weeks 

 after the practical elimination of soil pollu- 

 tion. After six weeks only a very few larvse 

 were left. In a large series of laboratory 

 experiments carried out with different soils 

 and under different conditions, there was a 

 great reduction in numbers of larvse after 

 from two to three weeks and an almost com- 

 plete dying out in six weeks. These findings 

 which are contrary to the present conception 

 of the length of life of infective hookworm 

 larvse indicate that under tropical conditions, 

 the larvse will die out quickly in the soil 

 after the elimination of soil pollution by in- 

 fested individuals. 



William W. Cort 



Johns Hopkins University, 

 Baltimore, Md. 



THE AMERICAN ASSOCIATION FOR 

 THE ADVANCEMENT OF SCIENCE: 



THE TORONTO MEETING 



The second Toronto meeting of the Ameri- 

 can Association and associated societies will 

 be very conveniently arranged in all its de- 

 tails and promises to be one of the most satis- 

 factory meetings in the history of the As- 

 sociation. The preliminary announcement of 

 the meeting has recently been sent from the 

 Washington ofiice to all members, and the 

 permanent secretary will send copies to all 

 who request them. 



The announcement, a 47-page booklet, 

 gives the personnel of the local committee 

 for the meeting (Dr. J. C. Fields, chairman; 

 198 College St., Toronto) and the list of the 

 chairmen of the twelve subcommittees that 

 have charge of local details, also the list of 

 tlie Toronto representatives of the various 

 sections. Many features of the meeting are 

 mentioned or described. The usual lists of 



