408 THE MICROSCOPE. 



in fig. 194, Nos, 1, 2, and 3. These revolving globular bodies are 

 found of various sizes, some large enough to be discernable by the 

 naked eye. 



Leeuwenhoek first perceived the motion of what he termed globes, 

 " not more than the 30th of an inch in diameter, through water ; and 

 judged them to be animated." These globes are studded with innumer- 

 able minute green spots at their surface, each of which is a cell about 

 the 3500th part of an inch in size, with a vivid nucleus having many 

 ever-active cilia, that bristle over their spherical home and are bound to 

 each other by bands forming a beautiful network. Within this globe, 

 busy active nature is at work carefully providing a continuance of the 

 species ; and from six to twenty little bright-green spheres have been 

 found enclosed in the larger transparent case. As one of these arrives 

 at maturity, the parent cell enlarges j then bursts asunder to launch 

 forth its offspring into a watery world. Both the older and younger 

 spheres possess openings through which the water freely flows, affording 

 food and air to the little organised beings. 



Dr. Carpenter says, "The Volvocince, whose vegetable nature has been 

 made known to us by observation of certain stages in the history of 

 their lives, are but the motile forms (Zoospores) of some other plants, 

 whose relation to them is at present unknown." 



Professor Williamson, having carefully examined the Volvox globator, 

 has shown that the increase of internal cells is carried on in a manner 

 precisely analogous to that of the algae ; that between the outer inte- 

 gument and the primordial cell-wall of each cell a hyaline membrane 

 is secreted, causing the outer integument to expand ; and as the prim- 

 ordial cell-wall is attached to it at various points, it causes the internal 

 colouring-matter, or endochrome, to assume a stellate form (see fig. 

 194, No. 3), the points of one cell being in contact with those of the 

 neighbouring cell, these points forming at a subsequent period the 

 lines of communication between the green spots generally seen within 

 the full-grown Volvox. Cilia can be distinctly seen on the outer edge of 

 the adult Volvox ; by compressing and rupturing one, they may even 

 be counted. Mr. Busk has been able to satisfy himself, by the addition 

 of the chemical test iodine, of the presence of a very minute quantity 

 of starch in the interior of the Volvox, which he considers as conclusive 

 of their vegetable character. A singular provision is made in the 

 structure of the gemmules, consisting of a slender elastic filament, by 

 which it is attached to the parent cell-wall : at times it appears to 

 thrust itself out, as if in search of food ; it is then seen quickly to re- 

 cover its former nestling-place by contracting the tether. 



