260 MICROSCOPIC FOEMS OF VEGETABLE LIFE. 



them as each possessing a mouth, several stomachs, and an eye ! 

 Our present knowledge of their nature, however, leaves no doubt 

 of their Vegetable character ; and the peculiarity of their history 

 renders it desirable to describe it in some detail. 



158. Each of the so-called "Monads" is in reality a some- 

 what flask-shaped mass of endochrome, about l-3000th of an 

 inch in diameter; consisting, as in the previous instances, of 

 chlorophyll-granules, dilFused through a colorless protoplasm 

 (Fig. 70, I, l) ; and bounded by a layer of condensed protoplasm, 

 which represents a primordial utricle, but is obviously far from 

 having attained a membranous consistence. It is prolonged out- 

 wardly (or towards the circumference of the sphere) into a sort 

 of colorless peak or proboscis, from which proceed two long 

 vibratile cilia (l) ; and it is invested by a pellucid or " hyaline" 

 envelope (i, d) of considerable thickness, the borders of which 

 are flattened against those of other similar envelopes (e, c c), 

 but which does not appear to have the tenacity of a true mem- 

 brane. It is impossible not to recognize the precise similarity 

 between the structure of this body, and that of the motile " en- 

 cysted" cell of Protococcus pluvialis (Fig. 68, k) ; there is not, 

 in fact, any perceptible diflerence between them, save that which 

 arises from the regular aggregation, in Volvox, of the cells which 

 normally detach themselves from one another in Protococcus. 

 The presence of cellulose in the hyaline substance is not indi- 

 cated, in the ordinary condition of Volvox, by the iodine and 

 sulphuric acid test, though the use of " Schulz's solution" gives 

 to it a faint blue tinge ; there can be no doubt of its existence, 

 however, in the hyaline envelope of what has been termed Vol- 

 vox aureus, which is in reality nothing but the " winter spore" 

 of Volvox globator. The cilia and endochrome, as in the motile 

 forms of Protococcus, are tinged of a deep brown by iodine, 

 with the exception of one or two particles in each cell, which, 

 being turned blue, may be inferred to be starch ; and when the 

 contents of the cell are liberated, bluish flocculi, apparently in- 

 dicative of the presence of cellulose, are brought into view by 

 the action of sulphuric acid and iodine. All these reactions are 

 strictly vegetable in their nature. When the cell is approaching 

 maturity, its endochrome always exhibits one or more " vacuoles" 

 (Fig. 70, I, a a), of a spherical form, and usually about one-third 

 of its own diameter ; and these " vacuoles" (which are the so-called 

 " stomachs" of Prof. Ehrenberg) have been observed by Mr. G. 

 Busk to undergo a very curious rhythmical contraction and dila- 

 tation at intervals of about 40 seconds ; the contraction (which 

 seems to amount to complete obliteration of the cavity of the 

 vacuole) taking place rapidly or suddenly, whilst the dilatation 

 is slow and gradual. This curious action ceases, however, as the 

 cell arrives at its full matui'ity ; a condition which seems to be 

 marked by the greater consolidation of the primordial utricle, by 

 the i-emoval or transformation of some of the chlorophyll (the 



