—— 116 
and easily escape observation, when the fe- 
males are not numerous. Slight or recent in- 
fections cannot be safely excluded, as the 
eggs take some time to reach the intestine, 
when they are not altogether retained, which 
seems to happen frequently. y 
Examination is rendered easier by wa- 
shing the feces, followed by sedimentation or 
centrifugation. With these may be combined 
the use of wire netting or muslin which re- 
tain the larger bodies. Thus we obtain a se- 
- diment that contains almost exclusively glo- 
bules of starch and eggs of parasites which 
easily found. 
The appearance of the egg is well per- 
ceived in our illustrations. The normal eggs 
(Fig. 15). are furnished with a lateral spine 
only and contain a perfectly visible embryo. 
In pathological eggs the size may be dimi- 
nished while no embryo is found. One of 
the poles may show a protrusion, more or 
less considerable (Figs. 10 and 11), but this 
could only be taken for a terminal spine 
when the examination is carelessly made. 
As yet there has been no mention of two la- 
teral spines. Figure 12 shows the only case 
of this rare anomaly which I found while 
examining thousanás of eggs. The eggs, with 
or without embryo, may be calcified or en- 
crusted with crystals. (Figs. 9,13 & 14). Re- 
cent descriptions of eggs with lateral spines 
have been published by HOLCOMBE and 
GONCALEZ-MARTINEZ. Both have illustra- 
trations which are rather schematic, especial- 
ly those of the latter. 1 also show a drawing 
from nature. The outside shell of the egg or 
chorion has aregular oval form, interrupted 
only by the apex of the spine, which is sharp 
and compact, whilst the base is conical and 
hollow. 
The dimensions of the eggs are rather 
variable in the normal state. HOLCOMB. gives 
112 to 162 for the larger axis and 60-70 for 
the lesser. Taken from thirty measures, GON- 
CALEZ-MARTINEZ indicates a medium of 
147f or 67, 69. These dimensions agree better 
then those of the spike, of which the length, 
according to the first author, is 15-17, against 
22,7 of the latter, and the width 7,5, but this 
may be due to the way of measuring. The 
point of insertion, according to HOLCOMBE, 
is distant from the nearest pole for the fourth 
part of the longitudinal axis. 
The interior membrane (amnion or vitel- 
lary membrane) is near the other, but does 
not enter the spine and leaves an enlarge- 
ment of varying thickness at the poles; as a 
rule, it is generally larger at the pole farther 
from the spine, which many be considered the 
anterior, as it is generally occupied by the 
cephalic extremity of the embryo. Thus the 
spine points backwards. 
Both membranes are fine and transpa- 
rent, but while the chorion is more yellow- 
ish, the amnion is hyaline; this pigment 
however, as in other eggs of entozoa, is de- 
rived from the fecal medium, and is absent 
in the eggs protected by a thick covering of 
mucus. 
The embryo or miracidium inside the 
ripe egg. 
The normal eggs are voided with the 
embryo alive and completely formed. The 
transparent membranes do not prevent exa- 
mination, but weak powers do not allow of 
the distinguishing of all structural details. 
Using immersion lenses, the cover glass must 
be fixed on the slide, which may be done 
with paraffine or turpentine. Thus we may 
obtain clear images, but the outlines of the 
internal organs are very delicate and their su- 
perposition prevents their being seen all in 
one egg. The embryo is covered with cilia 
which in the anterior part are longer and 
point forwards. The bucal papillais bare and 
on the rest of the body the cilia are turned 
backwards. 
There are four tubular openings, of the 
excretory system showtng vibrating mem- 
branes, perceived in some extension. 
The existence of contractile fibres, run- 
ning in two or three different directions, is 
indicated by the lively movements the embryo 
makes before bursting its shell. They are not, 
however, so easily seen and demonstrated, as 
