ae The Philippine Journal of Science 1915 
allowed to cool. They were all killed. This point undoubtedly 
is of considerable practical importance in preventing the spread 
of infection. Many fruits and vegetables which are commonly 
eaten raw can be dipped into water at this temperature without 
being injured. 
Moderately low temperatures simply retard the development 
without killing the eggs. Eggs kept for twenty-four days at 
a temperature between 5° and 12° showed no traces of devel- 
opment. At the end of that time they were placed in the lahbo- 
ratory at ordinary temperature and developed into adult embryos 
in fourteen days in the same medium in which they were kept 
throughout the experiment. 
THE HATCHING OF EMBRYOS 
The embryo, when ready for hatching, is a small worm with 
a blunt anterior and a pointed posterior end. It is coiled in 
the shell and moves almost constantly as long as it is alive. 
It is from 0.12 to 0.20 millimeter long and from 0.014 to 0.02 
millimeter in diameter. In tap water and in salt solution the 
embryos remain active for from one to three weeks. On damp 
earth and in water which contains a large number of alge a 
great many of the eggs hatch, but the young worms die very 
soon. 
In a recent paper A. Martin * presents some very interesting 
results of work on the eggs of Ascaris from the calf, pig, horse, 
and dog. He conclusively proves that the embryos of these 
ascarids hatch best in alkaline solutions, and that when devel- 
oped eggs are introduced into the alimentary canal of an animal 
they pass through the stomach unaffected and only hatch after 
they have been subjected to the action of the alkaline juices in 
the intestine. He finds also that none of the juices of the ali- 
mentary canal are able to digest the chitinous layers of the 
shell, that the embryos always emerge through a V-shaped 
opening which appears in the end of the shell, and that the 
shell passes out, undigested, with the feces. He is of the opin- 
ion that the hatching is due to stimulation of the embryos by 
the alkaline substances in the intestine and by the increase in 
temperature, and not to any action of the juices on the structure 
of the shell. 
He found also, in the cases of the embryos of the calf and 
of the pig ascaris, that it was necessary for the embryos to be 
completely developed before being fed to an animal, or placed in 
* Ann. d. Sci. natur. (1918), Nos. 1 and 2. 
