F. H. Stewart 
193 
middle and posterior thirds of the body between the intestine and the 
ventral line (Fig. 5). It consists of a clearly defined lens-shaped group 
of cells. 
The early life history of Ascaris mystax Zeder (A. marginata Rud.). 
The development of the eggs of the Ascaris of the cat and dog has 
been studied by Nelson, Verloren, Davaine, Baillet and Grassi (Railliet, 
Traite de Zoologie Med. et Agric.) and by Leuckart ( Menschl. Parasiten, 
n. pt. 2, p. 275). I regret that at present I have not access to the works 
of these authors with the exception of the last-named. 
Segmentation and the formation of an active embryo have been 
found to take place in water and damp earth. Davaine (quoted by 
Leuckart) states that development takes place also in a dry condition. 
Leuckart gives the period necessary for the formation of an active 
embryo in summer as four to ten weeks and in winter several months. 
The fully formed embryo differs from that of A. lumbricoides in being 
larger, 0-36-0-42 mm. in length as compared with 0-3-0-38 mm. in the 
latter, and in bearing a more distinct boring tooth on the ventral aspect 
of the mouth. There are no signs of the oesophageal bulb of the 
adult with the exception of a slight swelling of the posterior end of the 
oesophagus. He gives a figure of the embryo. 
This investigator did not succeed by any means in bringing about 
the hatching of the eggs, nor did he produce any further development 
by feeding experiments. At one time he considered that he had 
empirically caused direct infection since he found young worms 3-4 mm. 
in length in the intestines of dogs which had been kept a long time in 
a kennel on the floor of which he found embryo-containing eggs. 
Repeated attempts at artificial infection in more than two dozen cats 
and dogs gave however negative results. He then attempted to find 
an intermediate host. He administered eggs of the worms to rabbits 
and mice and examined these animals after several weeks hoping to 
find encapsuled nematodes. No such nematodes were found. He 
states that the eggs passed unaltered through the alimentary canal of 
the mice. 
In a later experiment he placed a number of young cats in a particular 
dwelling in which a number of animals had recently been kept. The 
latter had been found to harbour numerous young Ascarids. The cats 
were fed on bread only. After six to eight days the cats were killed. 
They proved to be infected with Ascarids 4-8 mm. long. In the stomach 
of one of them, a kitten eight weeks old, forty to sixty nematode larvae 
