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. 



