664 The Philippine Journal of Science 1922 
dishes containing a thin layer of 2 per cent formalin (Plate 1, 
figs. 9 and 10). Formalin cultures ten to twelve days old 
contain embryonated eggs (Plate 1, figs. 11 and 12), the embryos 
generally exhibiting sluggish movements. 
In common with the behavior of embryonated eggs of other 
species of Ascaris, further development does not take place 
unless the eggs are swallowed by a suitable host. Occasionally, 
dead larve have been observed in culture dishes, but hatching 
outside of the host is an unusual occurrence. 
The vitality of the eggs of Ascaris vitolorum was considerably 
reduced after two months, during which time they were kept 
in 2 per cent formalin at room temperature. Although many 
eggs still showed vitality in response to heat stimulation, they 
produced very light infestations in experimental animals to 
which they were fed. Examination of feces from such experi- 
mental animals, two or three days after artificial infection, 
revealed the presence of numerous embryonated eggs, appar- 
ently dead. Whether the eggs normally have a short duration 
of life or whether the growth of fungi in culture dishes is a 
factor in shortening their life hag not been determined. 
Experimental feeding of ripe eggs to rats and guinea pigs re- 
sulted in the hatching of viable eggs and the elimination of the 
eggshells and of undeveloped eggs with the fxces. Empty egg- 
Shells eliminated with the dejecta of the alimentary canal were 
invariably broken (Plate 1, fig. 14) , thus proving that the hatch- 
ing of the eggs is the result of the activity of the embryos, whose 
escape from the shell involves the rupture of the latter. Un- 
developed eggs passed through the alimentary canal intact (Plate 
1, fig: 13). 
Eggs of Ascaris vitolorum do not hatch in the stomach, as 
the following observations will show. Within two hours after 
forced feeding of eggs to guinea pigs, numerous unhatched eggs 
were found in the stomach, hatched and unhatched eggs as well 
as larve were found in the small intestine, whereas most eggs 
that were found in the large intestine and ceca were un- 
developed. ; 
That hatching of eggs is due to the activity of the embryos 
rather than to the passive effects of the intestinal environment 
is further shown by the results of feeding to experimental 
animals old cultures of embryonated eggs many of which were 
nonviable. After artificial infection with these eggs large num- 
bers of dead embryonated eggs were found in the feces of ex- 
