ROTATION OF FLUIB IN CLOSTBRIUM. 



267 



growth of these plants, as in other Algse, starch is produced ; the 

 presence of which is made obvious by the appHcation of iodine. 

 There is no one essential point, therefore, in which the Desmi- 

 diacece differ from other Protophytes, or really approach the 

 Animal kingdom. Some of the arguments that have been ad- 

 vanced in support of their Animal affinities, — such as their mul- 

 tiplication by transverse subdivision, and their generation by a 

 process of conjugation, — are really, now that the physiology of 

 the unicellular plants is better understood, much more strongly 

 indicative of their Vegetable alliances. The assertion of Prof. 

 Ehrenberg, that Closterium possesses organs which it protrudes 

 through apertures in its extremities, and keeps in continual 

 motion, is (like too many of his statements) simply untrue. And 

 although many of these plants have a power of slowly changing 

 their place, so that they approach the light side of the vessel in 

 which they are kept, and will even traverse the field of the 

 microscope under the eye of the observer, yet this faculty is in 

 no respect different from that which many undoubted Proto- 

 phytes (such as Oscillatorice, § 196) possess. 



164. A very peculiar feature which has recently attracted much 

 attention, is the circulation of fluid which may be seen to take 

 place in the Closterium, both between its " cellulose" coat and its 

 "primordial utricle," and within the latter; and the ciliary action 

 by which, according to the testimony of some good observers, 

 this circulation is maintained. It is not difficult to distinguish 

 this movement along the convex and concave edges of the cell of 

 any vigorous specimen of Closterium, if it be examined under a 

 magnifying power of 250 or 300 diameters ; and a peculiar whirl- 



FiG. 72. 



Economy of Closterium lunula:— Xf frond showing central separation at a, in which large glol)ulea. 

 &, are not seen; — b, one extremity enlarged, showing at a the double row of cilin, at b the internal 

 current, and at c the external current," — c, external jet produced by pressure on the frond; — d, frond 

 in a state of self-division. 



ing movement may also be distinguished, in the large rounded 

 space which is left at each end of the cell by the retreat of the 



