DESMIDACE^E. 409 



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

 functions of vegetable life namely, absorption, assimilation, exhala- 

 tion, secretion, reproduction, &c. 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 performance 

 of different offices, the functions of which are effected by the agency of 

 cells, obtaining materials of formation 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 fofr the First Great 

 Cause."* 



DESMIDACE^E. 



The disputed question of the animal or vegetable nature of these 

 cells has received much valuable elucidation from Mr. Ralfs, who has 

 given to the world the results of his laborious researches in his excel- 

 lent work on The British Desmidiece, published in 1848 ; and the con- 

 clusions of this painstaking author have been generally accepted by 

 men of science. The interest which has so long attached to this topic 

 will warrant us in devoting some space to its consideration ; and we 

 avail ourselves for that purpose of Mr. Ralfs' labours, with a recom- 

 mendation to those of our readers who would wish to familiarise them- 

 selves more completely with this peculiar species, to consult the pages 

 of the book above referred to. 



Desmidacece are grass-green in colour, surrounded by a transparent 

 structureless membrane, a few only having their integuments coloured ; 

 they are all inhabitants of fresh water. Their most obvious peculiari- 

 ties are the beauty and variety of their forms and their external mark- 

 ings and appendages ; but their most distinctive character is their evi- 

 dent division into two or more segments. Each cell or joint in the 

 Desmidaceae generally consists of two symmetrical valves or segments ; 

 and the suture or line of junction is in general well marked. The mul- 

 tiplication of the cells by repeated transverse division is full of interest, 

 both on account of the remarkable manner in which it takes place, and 

 because it unfolds the nature of the process in other families, and fur- 

 nishes a valuable addition to our knowledge of their structure and phy- 

 siology. 



The compressed and deeply-constricted cells of Euastruin offer most 

 favourable opportunities for ascertaining the manner of their division ; 

 for although the frond is really a single cell, yet this cell in all its stages 

 * Dr. Mantell's Wonders of Geology. 



