140 THE MODE OF DEVELOPMENT 



plant does not, however, dissolve at once in order io allow the 

 ripened spores to escape, but an aperture (fig. 81, A, a) is formed 

 in the side of the finger-like projections, through which the young 

 glides forth to a freer life. This it enjoys for a few hours, and 

 then commences its career as a fixed plant. I will not now 

 describe the process of transformation into this latter condition, 

 but reserve it until we come to one of those plants in which I 

 have myself watched the development through all its changes. 



The most clearly defined step that is taken toward a higher 

 rank, is exhibited by the partitioning of the cavity of the 

 single plant into several chambers. This we have in the sea- 

 weed, of which a portion is delineated here 

 (fig. 82, A). It is called Cladophora. These 

 three cavities, separated from each other by 

 these double diaphragms, (c,) have each an 



aperture, (a, a 1 ,) through which the spores 

 (B) are escaping. The whole plant, which 

 branches considerably, is made up of similar 

 cells, in all of which, Thuret says, spores 

 are developed, and from which they event- 



w 



Fig. 82. ually escape. The entire plant, from top to 



bottom, becomes a mass of seeds. It is merely a branching 

 string of one-celled plants, each one of which is formed in the 

 likeness of the snow-plant, Protococcus. What, in addition to 

 its vibrating lashes, renders the zoospore all the more like cer- 

 tain of the Infusoria, is a red spot in the clear space at the 

 pointed end. This has been mistaken for and identified with 

 the eye-spot of certain animalculse, such as Euglena, (fig. 86,) 

 &c. ; but Thuret has shown it to be a mere globule of oily mat- 

 ter, and that, moreover, it is not always present, or is more or less 

 indistinct. 



The next decided advance in rank is exhibited by those plants 



Fig. 82. Cladophora glomerata. Ktz. A, three of the joints or cells from 

 the end of the branch of a plant ; a, lateral apertures ; a 1 , terminal aperture ; 

 c, transverse partition; s, young plants germinating within the cell of the par- 

 ent; B, a zoospore magnified 330 diameters. From Thuret. 



