246 T. W. Engelmann on the Infusoria. 



is found to commence division after from six to ten hours' 

 union ; and this unloosing is at length completed, the resultant 

 individuals differing in no perceptible features from the ordinary 

 specimens of the species ; and, as far as Engelmann could make 

 out, all this marvellous process stood in no relation whatever 

 with sexual reproduction. 



The second variety of conjugation has already been described 

 by Stein in Stylonychia pustulata and S. histrio. In a not un- 

 common form of this partial conjugation, the two individuals 

 are found united only by their anterior extremities, and a repro- 

 duction of the ciliary apparatus of the ventral surface is seen to 

 proceed (PL III. fig. 5). This continues to extend itself, and 

 the adoral wreath of cilia especially stretches forward, whilst the 

 old adoral and frontal cilia become absorbed (fig. 6) . The act of 

 fission extends from behind forwards, until the separation is com- 

 plete (fig. 7y. All this is effected in such a way that the indivi- 

 dual on the right side retains the residue of the old frontal region 

 with its three largest bristles and the remnants of the old adoral 

 ciliary wreath; but these original parts themselves vanish in 

 another fifteen minutes. The nucleus has in the meantime un- 

 dergone various changes, and generally appears broken up into 

 several spherical segments. The beings resulting from these 

 metamorphoses resemble those of Euplotes Charon in being de- 

 stitute of a mouth and peristome, and in giving origin to those 

 peculiar corpuscles, having a large transparent central body, 

 w^hich are always found in company with the conjugated forms 

 oi Stylonychia pustulata. Engelmann followed up the observa- 

 tion of some such specimens, and found that, after a while, they 

 resumed the characters of the species, and proceeded to undergo 

 fission, or else, as in the case of some, they underwent the pecu- 

 liar process of encysting. 



Stylonychia histrio exhibits, in all essential particulars, the 

 same two forms of conjugation. 



Once, among various examples of Stylonychia histrio in conju- 

 gation, Engelmann met with an animalcule of the same species, 

 which exhibited, in the place of the nucleus, three large, clear, 

 discoid bodies, of which one possessed a central granular and 

 circular nucleus (PI. III. fig. 8). After rather more than an 

 hour, two of these bodies began to coalesce, so that, three 

 hours afterwards, the interior of the animal presented one much 

 larger discoid body, and behind this a smaller one ; but, twenty 

 minutes later, this last also first adhered and then ultimately 

 united with the other, so that in the end the individual presented 

 a single large spherical body having a granular central nucleus. 

 The further history of this animalcule could not be traced, as it 

 was lost to observation by death. 



