VOLVOCINEJJ. 193 



tain 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, says : 

 " That the increase of its internal cells is carried on in a 

 manner precisely analogous to that of the algse; that 

 between the outer integument and the primordial cell- wall 

 of each cell, a hyaline membrane is secreted, causing the 

 outer integument to expand; and as the primordial cell- 

 wall is attached to it at various points, it causes the inter- 

 nal colouring-matter, or endochrome, to assume a stellate 

 form (see fig. 120, 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, Professor 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, con- 

 sisting of a slender elastic filament, by which each is at- 

 tached 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 

 recover its former nestling-place by contracting the tether. 

 " Wonderful as it may appear, we have here an example 

 of all the functions of vegetable life namely, absorption, 

 assimilation, exhalation, secretion, reproduction, <fec. 

 effected by a single cell. This is ever continued in the 

 highest and most complicated orders of vegetable life, in 

 which there is a variety of organs adapted for the per- 

 formance of different offices, the functions of which are 

 effected by the agency of cells, obtaining materials of for- 

 mation and support from the ordinary chemical agents 

 around them. Thus the more man gains a knowledge of 

 the wonders displayed in these minute objects of creation, 

 the more is the mind humbled and inspired with reverence 

 for the First Great Cause." T 



(1) Dr. Mantell's Wonders of Geology. 

 O 



