436 M. T. Thoi-ell on the Species of the Argulidcje. 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 3.54 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.— Ora Two European Argulidse, with Remarks on the Morphology of the Argulidse and their Systematic Position, to-gether with a Review of the Species of the Family at present known. By T. Thorell. [Concluded from p. 286.] IV. I SHALL now pass in review the species of Argulidse hitherto known, although many of them are so incompletely described that it is not without difficulty that they can be determined.
LVI.—On two European Argulidæ, with remarks on the morphology of the Argulidæ and their systematic position, together with a review of the species of the family at present known
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