204 
Ascaris lumbricoides 
largely unicellular, but some 2-6 cell stages occur. On the 7th day the 
eggs are in advanced segmentation. No experiment was conducted 
with eggs in human faeces placed on the ground as in Expt. 8 with pigs’ 
faeces. The rapidity and extent of development is determined by the 
degree of aeration and dampness of the nidus (Expts. 2-6). Eggs of 
Ascaris lumbricoides, which remain in human faeces, do not lose their 
power of full development on removal to a more favourable nidus. It 
is therefore probable that they could complete their development in 
human faeces lying on the ground in the open air. 
(2) In the Faeces of the Pig. 
Full development can take place in the faeces of the pig when com¬ 
pletely exposed to the air and kept moderately damp (Expt. 8). In 
this nidus development is as rapid as in the case of eggs washed and 
kept in a damp atmosphere. Fully developed embryos are found on 
the thirteenth day after evacuation. 
(3) In contaminated Water.. 
Numerous observations were made on eggs washed out of human 
faeces and kept in the contaminated water. In no case was any develop¬ 
ment observed. 
(4) In uncontaminated Water. 
Eggs removed directly from the uterus and placed in tap water can 
reach full development, but as Leuckart pointed out development is 
extremely irregular in point of time and a large proportion of the eggs 
undergo no development whatever. 
(5) On the surface of the Soil. 
In nature, conditions of thorough exposure to air and dampness, 
without actual immersion in water, are found in the superficial layers 
of the soil. Eggs of A. lumbricoides, removed directly from the uterus, 
and placed on the surface of moist clayey earth, were found to reach the 
vermicide and early vermiform embryo stages on the tenth day, and 
the stage of fully formed embryo on the twelfth day, the temperature 
and humidity being that of Hong Kong in the summer: 80-90° F. 
and humidity about 90 %. 
