94 



THE AMERICAN MONTHLY 



[May, 



ACTION OF VARIOUS REAGENTS ON VIBRATILE QllAh.— Continued. 



however, that the same phenomena 

 are of frequent occurrence as well in 

 the vegetable kingdom. Besides sim- 

 ilarity of structure, the functions of the 

 cilia are much the same in both king- 

 doms. They are, as a rule, slender, 

 conical ha.irs, homogeneous through- 

 out, smooth, colorless, uniaxial and 

 doubly refractive, the optical axis 

 always coinciding with the direction 

 of greatest length. They possess a 

 tolerable firmness, pliability and elas- 

 ticity. They cannot be considered as 

 protuberances of the cell wall, but 

 pass through it, having their origin in 

 the outer layer of the contained pro- 

 toplasm — the ectoplasm. As in the 

 animal kingdom, the number of cilia 

 attached to a single cell, varies from 

 a large number, forming a tuft or 

 crest, to a single, usually very long, 

 hair. Movements of cilia situated 

 upon the same cell are isochronous. 

 Cilia are found attached to fixed cells, 

 (yGoninm, Volvox, SfephanosphcEra, 

 jPaudorina, and the Heterocysts of 

 Nostocacea;), or to freely motile cells, 

 causing by their mechanical action the 

 locomotion of the whole family or of 

 the single cell, as the case may be. 

 Corresponding to the animal sper- 

 matozoids, which are only peculiar 

 modifications of epithelial cells, are 

 the vegetable antherozoids. The origin 

 of the force employed in ciliary motion, 

 is, as we have noticed in a previous 



chapter, undoubtedly the same for 

 both animal and vegetable cells. 



The Movements of Vegetable 

 Protoplasm. — (A.) I'hose move- 

 ments which occur within the cell- 

 wall, as circulation and rotation. (B.) 

 The movements of free, naked, proto- 

 plasmic bodies, viz : amoeboid and 

 ciliary movements. 



It is to the latter group that we 

 have our attention directed, and es- 

 pecially to that section of it, in which 

 the movements produce no change in 

 the external form of the cell, that is, 

 to ciliary movement brought about by 

 the rapid lashings of minute whip- 

 like appendages (zoospores, swarm- 

 spores, &c.,) or by the undulations of 

 filiform, primordial cells, each of 

 which, in so far as its movements are 

 concerned, is no more than an isolated 

 ciliuni, (antherozoids and spermato- 

 zoids). While in a number of cases 

 we may observe ciliary motion accom- 

 panying the plant throughout its 

 adult existence, we find it chiefly 

 employed as a temporary means, for 

 the diffusion of particles engaged in 

 the reproduction of species. Ciliary 

 motion in plants is confined to the 

 cryptogams, and it is only in the very 

 lowest of these, that it occurs in the 

 adult plant. It accompanies both 

 asexual and sexual reproduction, 

 which we will take up separately, — 

 examining its manifestations in each. 



