138 
Heligmosomum muris Yokogawci 
Table II. 
Measurements of Larvae of H. muris in the Infective Stage. 
18 clays after culture 
(in faeces) 
14 days after culture 
(in faeces) 
Length 
Width 
Buccal-cavity Oesophagus 
Position of 
Tail 
(depth) 
(length) 
excretory pore 
(length) 
(mm.) 
(mm.) 
(mm.) 
(mm.) 
(from ant. end) 
(mm.) 
, 0-080 
0-028 
0-0125 
0-140 
0-130 
0-047 
0-715 
0-026 
0-0110 
0-148 
0-132 
0-042 
J 0-745 
0-026 
0-0120 
0-148 
0-137 
0-045 
0-630 
0-025 
0-0100 
0-152 
0-135 
0-043 
f0-760 
0-030 
0-011 
0-154 
0-132 
0-050 
( 0-652 
0-026 
0-011 
0-129 
0-134 
0-044 
0-680 
0-026 
0-012 
0-135 
0-130 
0044 
) 0-712 
0-027 
0-012 
0-148 
0-132 
0-046 
0-700 
0-027 
0-012 
0-138 
0-135 
0-046 
,0-65 
0-027 
0-011 
0-130 
0-132 
0-044 
Activities of the mature or infective larvae. The mature larvae usually are 
found along the edges of the filter paper, where they extend themselves in 
the air and wave back and forth slowly. They appear like minute hairs along 
the edge of the paper. If they are removed into water, they move actively 
as compared to the movement in the first stage. Their movement can best 
be described as “swimming.” They are more resistant than the younger larvae 
to all the influences of the environment. They are, however, less resistant 
than the mature larvae of other Strongylidae which are enclosed in protective 
sheaths. 
3. The Influence of the Environment on the Eggs and Larvae. 
From my experience in culturing the larvae of H. muris I learned the 
following facts in regard to the effect of environment. 
(a) Air. 
The eggs of Heligmosomum muris require a certain amount of oxygen for 
their development since they do not develop beyond the morula stage in liquid 
media of more than 0-2 cm. in depth, while the eggs hatch and the larvae 
develop normally in liquid media of less than 1 mm. in depth. 
I am of the opinion that more air is required during the development of 
eggs and larvae than for resting eggs and mature larvae, since the mature 
larvae were found alive for a long time even when kept in water at a depth 
of 1 cm. or more, while the developing larvae died under the same conditions 
in several hours to a few days according to the stage of their development. 
* (b) Light. 
The development of the eggs and larvae of H. muris cultured in faeces 
does not seem to be influenced to any extent by diffused sunlight, although 
darkness appears to be the most suitable condition for development. If 
cultures containing mature larvae are examined after they have been kept for 
a considerable time in darkness and compared with cultures which have been 
kept for a period in the light, the cultures from the darkness will show a larger 
