262 The Philippine Journal of Science 1921 
having verified the same in all points. When examined in a 
fresh specimen, the worm is easily made out as a transparent, 
colorless, snakelike organism, which wriggles about very actively 
among the blood corpuscles, but which does not rapidly pass 
out of the field of vision. It has a long, slender body, inclosed 
in a delicate, structureless sheath, in which it easily moves 
backward and forward. This body is blunt at the one end and 
pointed at the other. It is about 1/80 of an inch (0.317 mil- 
limeter) in length and 1/3000 of an inch (0.0085 millimeter) 
in breadth. It is most easily found with a 1-inch objective, but 
for the details a higher power must be employed. 
Carefully examined under a higher power and with the as- 
sistance of a staining reagent, a musculocutaneous layer is made 
out, in which delicate transverse striation can be discerned. 
An indefinite viscus can also be made out in the center portion 
of the worm, rather toward its posterior end. A shining V- 
shaped spot is clearly to be seen about the junction of the head 
fifth with the remaining four-fifths of the body. This spot is 
well shown .on staining with dilute hematoxylin, but is readily 
seen in unstained specimens. By staining, however, a second 
spot is also brought out a short distance from the tail, much like 
the first in form. The exact meaning of these spots is not 
quite clear, but it is suggested' that they are connected with 
development. In the interior of the musculocutaneous cylinder 
is a mass of cells whose nuclei are brought out well by staining. 
There is a break in this central column of nuclei at a spot just 
posterior to the anterior V-spot, but the significance of this 
break is not yet understood. 
The head is covered by a delicate 6-lipped prepuce, and a short 
fang is occasionally to be made out, protruding from the head, 
in specimens where the worm has almost ceased movement. 
One of the most notable things about these filarise is the 
feature that goes by the name of filarial periodicity. In the 
case of the embryos of Filaria bancrofti it is the rarest thing 
to find one of these in the peripheral blood during the day. 
About 5 or 6 o’clock in the afternoon a few begin to appear, and 
the number gradually increases until the maximum is reached, 
about midnight. The number then gradually diminishes until 
about 6 or 7 o’clock in the morning, when they disappear from 
the blood altogether till the following evening. If, however, 
the filarial subject be made to sleep during the day and rise at 
night, it is possible to reverse these conditions and cause the 
filarise to appear during the day instead of at night. In the 
