436 M. 'T. Thorell on the Species of the Argulide. 
attached to the pedicel) was also slightly indented, so that in 
outline it presented a guitar-shaped figure, each rounded half of 
which bore a pair of unequal cilia, and contained a contractile 
vesicle. In one minute more the contraction had increased to 
such an extent that the body was divided about halfway through. 
By 2.54 p.m. the animal had a dumb-bell shape, and the pedicel 
was attached to one of the segments near the point of con- 
striction. Still the process went on very rapidly, and by 2.55 p.m. 
the new bodies were widely separated, but still attached to each 
other by a mere thread. At 3 p.m. the body which was attached 
to the pedicel was left alone, and its companion swam away to 
seek a new attachment and build up its stem. 
To the last moment the hyaline envelope remained about the 
segments, and in fact so long afterwards that time and circum- 
stances did not allow me to ascertain its final disposition. I 
would remark, however, that when the ovate bodies of the half- 
grown monads are contracted temporarily into a globular shape, 
they appear identical (excepting that they lack the hyaline en- 
velope) with these recently fissated forms. In all probability, 
therefore, the latter lose their envelope and assume the shape of 
the former. 
As to the development of the stem, I think it quite certain 
that it grows out from the posterior end of the body. The best 
proof of this is, that I have frequently found a monad (especially 
in the condition of the one which I described above as breaking 
loose from its companion) nearly sessile upon a clean spot, and 
attached by a very short, faint, film-like thread. From this 
size upward I had no difficulty in finding abundant examples as 
gradually increasing in diameter as they did in length—thus 
furnishing a pretty strong evidence that the stem grows under 
the influence of its own innate powers, and is not, therefore, a 
deposit emanating from the body of the monad, except, perhaps, 
as far as it may be nourished by a fluid circulating within its 
hollow core. 
LVI.—On Two European Argulide, with Remarks on the 
Morphology of the Argulidee and their Systematic Position, to- 
gether with a Review of the Species of the Family at present 
known. By T. THore. 
[Concluded from p. 286.] 
Ty. 
I sHALL now pass in review the species of Argulide hitherto 
known, although many of them are so incompletely described 
that it is not without difficulty that they can be determined. 
