76 
dealing differs from 7. pediculus, and from any other hitherto’ 
known species. ; 
In particular they have not that hourglass form seen s0 
frequently in 7. pediculus, either when found on the tentacles of 
Hydra, or on the branchize of the larva of 7Zriton. They always 
retain a dome-like form (fig 2). I do not consider that this 
persistency of form is due to the sickly condition referred to by 
other writers in the case of 7. pediculus, as all the specimens I have’ 
found have been to all appearances in a very healthy state. Again, 
the number of the denticles exceeds those of 7. pediculus ; the 
ring of the acetabulum of the former consisting of thirty, whereas 
that of 7. pediculus has twenty-six. Its endoplast is band-like and 
curved, and the cuticle offers a greater resistance to the action of 
acetic acid than the denticles. The pulsations of the contractile 
vesicle are very sluggish. 
When the creature is treated with picro-carmine I find that 
the acetabulum gives way, and the whole of the contents of the 
interior are ejected, thus leaving the lorica empty (fig. 6). The 
acetabulum is articulated to the body, and is easily detached by - 
careful manipulation of the compressorium. The greatest length 
of the body is about 1/500 in., and the diameter 1/400 in. 
I have only to add that when I first found these creatures 
T thought that possibly they were peculiar to the pond from which 
I took the newts; since then, I have captured both species of — 
Batrachians in various ponds, within a radius of four miles of 
Canterbury, and found that they all harboured these parasites, © 
though in none did I find a single specimen of Hydra. The same 
result followed an examination of a dozen newts sent me by 
Mr. T. Bolton from Birmingham, the urino-seminiferous organs 
containing large numbers of the parasites. . 
- 
i 
EXPLANATION OF PLATE XVIII. 
Fig. 1.—Male organs of newt (after Owen), showing habitat of Trichodina, 
_ @, testes. c, efferent tubes. ¢, kidney. /f, urino-seminal canal. g, ureters. — 
Fig. 2.—Trichodina sp. lateral view x 500. 
Fig. 3.— e ventral view. al 
Figs 4 and 5.—Showing articulation of acetabulum (fig. 4 lorica, fig. 5 
acetabulum). oe 
Fig, 6.—Illustrating action of picro-carmine on the living subject, showing 
lorica partially disintegrated, acetabulum detached, and ejected endoplasm. 
Fig. 7.—Trichodina in situ on Hydva (Saville Kent). 
