280 Infusorial Circuit of Generations. 



a dry surface (e. g. by their undulating floss), instead of forming 

 into a dry scab, suddenly become liquid (like fusing lead), with an 

 immense internal commotion of parts, and bodily dissolve into such 

 cloud-molecules. The " wool " itself becomes quasi-' dropsical," 

 and each single fibril diffluent into a series of such uniform globular 

 molecules, which at first are endowed with an independent motion, 

 vibrio-like. Besides this, most of the encystments, moultings and 

 yolk-extrusions take place under the isolating cover of that uniform 

 protoplasm-membrane, which seems to exale a sort of bituminous 

 odour (hke the fumes of burning flesh, sun-baked carrion, or the rank 

 smell of miry river banks). Membranes, as thin but chemically 

 homogeneous organic substances, being impermeable to certain gases, 

 while permeable to others, a good deal of physiological interest is 

 involved in the study of this protoplasm-membrane, and its relation 

 to the swamp-gases. The particles of the nubecula are uniformly 

 globular. 



After repeated cross-segmentations, these undulate fimbriate 

 bodies, always revolving about the long axis (while evidently travel- 

 ling onward by the action of the ciliate mouth) divide lengthwise, 

 from below upward; thereby becoming somewhat purse or tear- 

 shaped ; the mouth being split in two, so that both stand " plying " 

 mouth to mouth, while yet connected at their foreheads, as it were. 

 These finally tear asunder by indentures, after which each has the 

 shape of a crooked glass-tear. When more adult, and about Vg- of 

 a line long, the internal yolks and designs have disappeared ; the 

 sarcode assumes a uniform yellowish tinge ; its mouth forms deep 

 cavities, while its front is toppling over like the hood of an Indian 

 turnip {Arum tri/phyllum) or of a Sarracenia leaf. It now con- 

 tracts to a globe and encysts. When a .smooth, transparent crust is 

 formed, gradually an inward gyration of cilia (as of an enclosed 

 centipede), which ultimately becomes very violent, is observable ; 

 and at last the excessive fatigue of watching this tantalizing gyra- 

 tion may be rewarded by seeing the inmate emerge, either as quite 

 a large but excessively limber, fluttering and transparent, full-size 

 single Oxytricha ; or else several smaller, mostly narrow, triangular 

 slips* escape, with the same exceedingly restless volubility ; the 

 marginal bristles not yet being stiffly extended in a plane, but 

 ruffled up and down hke the bristles on the undulating borders of a 

 thistle-leaf. As they feed and the tissues become scatent, the en- 

 tire form of an Oxytricha is presently acquired. 



I have observed still another development of Oxytricha ; its first 

 source, however, being as yet unknown to me. There appear on 

 the field of action numbers of quaint-looking, big-eyed balls, about 

 y^^ line thick, snouted, as it were, with a sort of " hair-lip " re- 

 sembhng a duck's bill; the stiff bristles within the bill-shaped 

 * The figures L and M, p. 447, in Carp. * Micr.,' seem to belong here. 



