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LIFE HISTORY OF ASCARIS LUMBRICOIDES. 5 
left exposed to the sun in India for 6 weeks contained actively motile 
embryos at the end of that time. We have kept the eggs of Ascaris 
suum in an incubator at 37° C. until they became extremely dry, but 
there was no continuation of the development when the eggs were 
moistened and removed to a lower temperature. Though dryness 
may be fatal to the eggs of Ascaris, it is certain that under most 
climatic conditions there is sufficient moisture in the environment 
(usually the soil) into which the eggs come after elimination from 
the host to enable development to proceed, at least intermittently, 
if not continuously. The inhibiting effect of the lack of moisture 
and the stimulating effect of its presence may be easily observed by 
placing newly deposited Ascaris eggs in water on a slide under a 
cover glass, noting the stage of development and then allowing the 
preparation to dry naturally. In a few days, if water is added to 
the: preparation, little or no further development will be seen to 
have occurred, but if the slide is kept moist for a few days it will 
be found that development proceeds again. By moistening or drying 
development may be thus favored or hindered. 
As shown by Hallez (1885), oxygen is necessary to the development 
of Ascaris eggs. This is indicated by the fact that eggs in water 
covered by a film of oil fail to develop. We -have observed that if 
the eggs are kept in stoppered bottles filled with water development 
is inhibited. According to Fauré-Fremiet (1912), the determining 
cause of segmentation is the oxidation of hydrocarbon reserves stored 
up in the egg, for which, of course, a supply of oxygen is necessary. 
Bacterial decomposition of the surrounding medium inhibits de- 
velopment and may be destructive to the vitality of Ascaris eggs. 
INCUBATING ASCARIS EGGS FOR EXPERIMENTAL USE. 
To secure the rapid development of a high percentage of Ascaris 
eggs to the final stage for experimental purposes, various methods of 
incubation have been used by different investigators. Martin (1913) 
obtained the most satisfactory results by placing the eggs in a 2 
per thousand solution of hydrochloric acid and incubating at a 
temperature of 33° C. Hallez (1885) spread the eggs over the sur- 
face of earth in a flowerpot which was kept moist by standing in 
water. After trying various methods and media we have adopted 
the following: The adult worms after collection are sorted by sex 
and size and only the larger females are retained. These are slit 
lengthwise and pinned out in a tray of water. The uteri are dis- 
sected out and removed. Twenty worms will furnish all the eggs 
that can be incubated in three petri dishes 138.5 centimeters in 
diameter. ‘The uteri are snipped with scissors into as small pieces 
as possible and are then rubbed up with a small quantity of 2 per 
cent formalin in a glass mortar. This forces the eggs out of the 
