74 
teased out with needles. The result was to confirm my previously 
formed opinion, that the animals were not endoparasitic in these 
organs. 
The alimentary canal was next detached its whole length, with 
a portion of the mesentery ; the latter was spread out and examined 
with 1 in. and 1/2in. objectives, but no signs of parasitic life were 
visible. The alimentary canal was also examined externally its 
whole length, and then placed in a perfectly clean trough with 
some of the distilled water. The intestine was very much attenu- 
ated, due to the fact that my stock had been kept short of food for 
afew days. It was then opened its whole length, and examined 
in sections. The cloaca was carefully examined, as the ureters 
and the urino-seminal duct (plate XVIII. fig 1, f and g) terminate 
in ashort canal, at the back of the cloaca. Not a specimen of 
Trichodina was, however, found either within the alimentary canal 
or in the fluid in which it was immersed. 
T next examined the testes and renal organs and their ducts. 
These were extracted, spread out on a’ glass plate under a lens, 
distilled water added, and examined by a1 in. objective. The 
testes were tolerably free, an occasional Trichodina being seen in 
their neighbourhood and among the efferent ducts. But it was 
otherwise with the renal organs; the fluid in their immediate 
neighbourhood was literally alive with the TZrichodina, which 
swarmed over the kidneys and amongst the ureters, at times 
detaching themselves and moving about, and then settling them- 
selves down and twirling round and round with a concentric motion. 
Here, then, amongst the urino-seminiferous organs, was the habitat 
of these ecto-endo-Zrichodina, a locality which, up to the present 
time, according to the authorities with which I am acquainted, had 
escaped the notice of old and recent investigators, the Zrichodina 
being looked upon as purely cctoparasitic and free-swimming in 
their habits. 
Having established the habitat of the organisms, I endeayoured 
to ascertain their relationship to the parasites of the Hydra. 
Hydre from a pond (known as the ‘“‘reed-pond’’) were ex- 
amined, and found free from Zrichodina pediculus; larvee of Triton — 
eristatus were taken from another pond at some distance, and 
specimens of Zrichodina were detached from the branchie, taken 
up with a pipette, and placed with the Hydre in a watchglass, a 
small quantity of water being added. Specimens of Zrichodina 
were then taken from a newly dissected newt, put into a watch- 
glass with a small quantity of water, and one of the Hydra added. 
The former was used as a control experiment, and attention was 
specially directed to the latter. 
' When placed in the watchglass the Hydra was of course con- - 
tracted, but after a few minutes elongated itself, and spread out its — 
