194 
Development of Ascaris 
were found which measured 0-4-06 mm. The stomach also contained 
fragments of straw and potato. No explanation could be given of 
the mode of entry of these larvae. No animal remains were found in 
the stomach or intestine to point to an intermediate host. 
Grassi (I quote from Railliet’s text-book) reared young puppies in 
a kennel soiled with egg-containing excrement. Their faeces contained 
Ascaris eggs on the 28th day and numerous Ascarids were found on 
section. A control experiment in sanitary surroundings proved nega¬ 
tive. Grassi concluded that infection was direct. 
Segmentation of the egg and development of the embryo. 
I made cultures of the eggs of A. mystax in a damp atmosphere at 
a temperature between 25° and 30° C. Under these conditions develop¬ 
ment proceeded as follows: 1st day. unsegmented to three-cell stage; 
2nd day, advanced segmentation; 4th and 5th days curved vermicules 
(the stage figured by Leuckart, Menschl. Parasit., ii. pt. 2, p. 213, 
fig. 8); 7th day, plump vermiform embryos; 8th day, active embryos. 
The intermediate host of A. mystax. 
Ripe eggs were administered to mice in their food. The details of 
the experiments are given below. Active Ascaris larvae were found 
in the liver between the 1st and 3rd days after infection. In Experi¬ 
ment 1 the eggs given on the 9th July were probably not old enough to 
be infective. The material at my disposal was unfortunately not 
large. 
Expt. 1. 9th July. Mouse N given eggs of A. marginata 6 days old containing 
vermiform embryos. 
12th July. Eggs of A. marginata 9 days old and of A. mystax 12 days old. 
13th July. Eggs of A. marginata 10 days old. 
14th July. Mouse N killed. No larvae in lungs or liver. 
Expt. 2. 14th July. Mouse P given eggs of A. marginata 11 days old. 
15th July. Mouse died 20 hours after infection. Eight larvae found in a 
portion of the liver, none in the lungs. 
Expt. 3. 29th July. Mouse U given eggs of A. marginata 26 days old. 
30th July. Killed. Larvae in the liver, none in the lungs. 
Expt. 4. 29th July. Mouse V given eggs of A. marginata 26 days old. 
1st August. Killed. One larva found in the liver, none in the lungs. 
Expt. 5. 4th August. Mouse Z given a small dose of eggs of A. marginata 
32 days old. 
9th August. No larvae in lungs or liver. 
