46 THE MICROSCOPE AND ITS REVELATIONS. 



( 418) as analogous to the sexual Generation of higher organisms. 

 Binary subdivision would seem to be universal among them; and has in 

 many instances been observed (as elsewhere) to commence in the nucleus. 

 The division takes place in some species longitudinally, that is in the 

 direction of the greatest length of the body (Fig. 305, D, E, F), in other 

 species transversely (Fig. 308, c, D), whilst in some, as in Chilodon cucul- 

 lulus (Fig. 306), it has been supposed to occur in either direction 

 indifferently. But it may be questioned whether, in this latter case, one 

 set of the apparent f fissions 'is not really ' conjugation ' of two indi- 

 viduals. This duplication is performed with such rapidity, under favor- 

 able circumstances, that, according to the calculation of Prof. Ehrenberg, 

 no fewer than 268 millions might be produced in a month by the 

 repeated subdivisions of a single Paramecium. When this fission occurs 

 in Vorticella (Fig. 305), it extends down the stalk, which thus becomes 

 double for a greater or less part of its length; and thus a whole bunch of 

 these Animalcules may spring (by a repetition of the same process) from 

 one base. In some members of the same family, arborescent structures 

 are produced resembling that of Codosiya (Fig. 296), by the like process of 



FIG. 306. 



Fissiparous multiplication of Chilodon cucullulus : A, B, c, successive stages of longitudinal 

 fission (?); D, K, F, successive stages of transverse fission. 



continuous subdivision. Another curious result of this mode of multi- 

 plication presents itself in the family Ophrydina ; masses of individuals, 

 which separately resemble certain Vorticellina, being found imbedded in 

 a gelatinous substance of a greenish color, sometimes adherent, and 

 sometimes free. These masses, which may attain the diameter of four or 

 five inches, present such a strong general resemblance to a mass of Nostoc 

 ( 247), or even of Frogs' spawn, as to have been mistaken for such; 

 but they simply result from the fact, that the multitude of individuals 

 produced by a repetition of the process of self-division, remain connected 

 with each other for a time by a gelatinous exudation from the surface of 

 their bodies, instead of at once becoming completely isolated. From a 

 comparison of the dimensions of the individual Ophrydia, each of which 

 is about l-120th of an inch in length, with those of the composite masses, 

 some estimate may be formed of the number included in the latter; for a 

 cubic inch would contain nearly eight millions of them, if closely packed; 

 and many times that number must exist in the larger masses, even mak- 

 ing allowance for the fact that the bodies of the Animalcules are sepa- 

 rated from each other by their gelatinous cushion, and that the masses 

 have their central portions occupied by water only. Hence we have, in 

 such clusters, a distinct proof of the extraordinary extent to which multi- 

 plication by duplicative subdivision may proceed, without the inter- 

 position of any other operation. These Animalcules, however, free 

 themselves a,t times from their gelatinous bed, and have been observed to 



