748 ON THE DEVELOPMENT OF BILIIARZIA HA5MATOBIA. 
naturally concluded that the embryos were killed outright, 
but here, to my surprise, the shock passed away in about half 
an hour, when they revived, and were soon afterwards hatched. 
One of the larvae thus set free carried off several of the loose 
intrachorional globules which had, during the period of trans¬ 
fixion, become firmly adherent to the ends of the caudal cilia. 
Here also I may remark upon a decided difference observable 
between the cilia of the head and body respectively. The 
former are at all times vibratile, active, and conspicuous; 
whilst the latter are more delicate, capable of comparatively 
little motion, and partaking more of the character of vibrissae. 
In length, their general measurement varies from ~ d \ rb " to 
The action of pure sea-water on the free animalcules, 
previously immersed in fresh or brackish water, was equally 
striking. All, without exception, immediately became para¬ 
lysed and almost motionless; nevertheless, on again adding 
fresh water, several entirely recovered. It is worthy of notice, 
also, that in these cases the cephalic cilia furnished the first 
indications of returning viability. I was particularly struck 
with the behaviour of one embryo, which, under the stimulus 
of the sudden shock, retracted its cone-shaped head almost 
entirely within the general cavity of the body (Figs. o,p). 
In their moribund condition, whatever shape the embryos 
retained, I observed that the sarcodic contents gradually 
faded away; the outline of the creature, however, becoming, 
for a time at least, even more marked than was normally the 
case. Usually, the body of the animalcule became consider¬ 
ably elongated whilst expiring in sea-water. Under other 
circumstances, as we have seen, the embryo frequently bursts; 
the sarcodic contents escaping in the form of amoeba-like 
bodies, and the cilia retaining their powers of movement long 
after all traces of the sarcode have disappeared. 
There are other points of interest connected with the 
appearances and distribution of the cilia, especially as fur¬ 
nishing diagnostic characters. The larvae of Bilharzia more 
closely resemble those of Fasciola hepatica than they do some 
of the more typical flukes. According to the recent observa¬ 
tions of Dr. Willemoes-Suhm (S. unci K. Zeitsch ., 1871, s. 181), 
the cilia of the embryos of the Bistoma megastoma , which 
infest various sharks, are limited to the anterior pole of the 
body. This is also the arrangement, as Leuckart first pointed 
out, in Bistoma lanceolatum. On the other hand, Pagenstecher 
has shown that the embryos of Bistoma cygnoides and Amphi- 
stoma (. Bijolodiscns) subclavatum are ciliated all over—an obser¬ 
vation which, as regards the latter species, has been amply 
confirmed by Wagner and others. Dr. Alex. PagenstecheFs 
