lilAT 10, 1907] 



SCIENCE 



735 



the life-cycle. This is probably due to a 

 reduction in size of the body unaccom- 

 panied by a proportionate reduction of 

 the ciliary apparatus. 



7. The general activity of the organism 

 varies greatly. During periods of high 

 division-rate, motion is exceedingly rapid, 

 and in a general way may be said to 

 diminish with the rate of division. 



8. Stimuli produce different effects at 

 different periods of the life-cycle. 

 K2HPO4, for example, accelerated the 

 division-rate of Gastrostyla steinii during 

 the early part and retarded it toward the 

 end of the life-cycle. 



Notes on the Life History of the Nematode 

 Hcemonchu.s contortii^: B. H. Ransom, 

 Bureau of Animal Industry, XJ. S. De- 

 partment of Agriculture. 

 Hcemonchus contortus, a nematode worm 

 of the family Strongylidte, which lives 

 parasitic in the fourth stomach of rumi- 

 nants is responsible for great losses among 

 sheep in the United States, especially 

 among lambs. The lambs become infected, 

 through the medium of the pasture, from 

 the adult sheep of the flock. Full grown 

 sheep may be heavily infested and show 

 little or no evidence of disease. Recent 

 studies in the zoological laboratory of the 

 Bureau of Animal Industry have brought 

 out a number of interesting facts in the 

 life history of H. contortus. The eggs of 

 the parasite hatch out in the droppings of 

 the host, and the embryos develop to the 

 final embryonic stage, known as the en- 

 sheathed stage, in a period of time varying 

 according to temperature, from three to 

 four days at 95° F., to three to four weeks 

 at 50° F. Ensheathed embryos crawl up 

 perpendicular surfaces whenever the air is 

 saturated with moisture, and by such mi- 

 grations gain positions on grass blades 

 when they are likely to be picked up by 

 grazing animals. Ensheathed embryos 



when swallowed by a sheep develop to 

 maturity in two to three weeks, but eggs 

 and embryos which have not reached the 

 ensheathed stage are not infectious when 

 swallowed. The eggs and newly hatched 

 embryos are quickly killed by freezing or 

 drying, but ensheathed embryos suffer no 

 apparent injury from freezing and may live 

 in a dried condition for at least thirty-five 

 days. When the temperature is 40° F., 

 or below, the eggs remain dormant, and a 

 small percent may retain their vitality for 

 as long as two months, but none survived 

 three months in the experiments tried. 

 Embryos have been kept alive in cultures 

 at a temperature of about 70° F. for as 

 long as six months. Enclosures previously 

 pastured by infested sheep were still in- 

 fectious after remaining empty for seven 

 months, from November to June. It is 

 suggested that lambs may be kept from be- 

 coming infected with the parasite and the 

 flock in course of time freed from infec- 

 tion by moving the flock from one pasture 

 to another before the embryos have time to 

 develop to the ensheathed stage in which 

 they crawl upon the grass, the time being 

 determined by means of cultures of feces 

 from infested animals. Bach time the 

 flock is moved a culture is made by placing 

 a small quantity of feces with sufficient 

 water to make a thick paste in a wide- 

 mouthed corked bottle and the culture ex- 

 posed to out-door temperature. When 

 ensheathed embryos begin to crawl up the 

 inner surface of the bottle where they may 

 readily be seen with the aid of a hand 

 lens, the sheep are moved to another en- 

 closure. 



On the Place of Origin and Method of 

 Distribution of Taste Buds in Ameiurus 

 nielas: F. L. Landacee, Ohio State Uni- 

 vei*sity. 

 Taste buds appear simultaneously in the 



extreme anterior portion of the oral cavity 



