LESSON 3.] INTRODUCTION. 9 



the cilia are either quiet, or entirely disappear, and the animal most 

 frequently rushes from the spot. 



48. At the time that cilia appear at each extremity of the body 

 (Fig. 5), two mouths are formed, and the animal 



pursues its prey, and receives food at both. But 

 still the constriction continues to advance, until the 

 body is nearly cut in twain the two portions being 

 joined by the merest pedicle (Fig. 6) ; presently this 

 becomes absorbed, and the two bodies, thus evolved 

 by spontaneous scission, swim off in contrary direc- 

 tions, never again to meet in this world ! 



49. Each half of the body, thus divided, is 



equally young, and rapidly attains maturity, which Development of the 

 is no sooner accomplished, than the same process is 

 repeated, and this continues without intermission in the Enchelis (and 

 allied animals), throughout the summer and autumnal months, until, 

 at the approach of winter, other modes of continuance of the species 

 are resorted to. 



50. Throughout these changes, however, it will be seen, that a 

 fair distribution is made of the germ cells (if such they be) ; one 

 half of the divided body may have a few more of them than the 

 other, but they visibly increase in both immediately, and continue so 

 to do till the time arrives for self- division. 



51. A mode of reproduction in the lower plants, is identical, in 

 every respect, to the spontaneous division of the body in the lower 

 animals. 



52. A species of Conferva, commonly called " Frog's spittle," 

 and erroneously supposed to be the ova of that animal, has been 

 watched, and carefully traced through corresponding developments. 



53. When the plant is first collected, it may consist of a long 

 chain of distinct cells (Fig. 7), each having a septum, or parti- 

 tion, at either extremity which separates it from the cell above, 

 and below (a, b) ; in the centre is a mass of endochrome (internal 

 green), or chlorophylle (green of a leaf), possessing a number of nu- 

 cleated spots (c). 



54. In a few days the cell would be seen to elongate considerably 

 (Fig. 8), and the mass of endochrome diffuse itself confusedly, with- 

 in the cell, till eventually it assumes the form of a beautiful double 

 spiral coil (a), the nuclei being greatly decreased in size. 



55. Presently, another phase presents itself; the cell becomes 

 still more elongated, and narrower (Fig. 9), the mass of endochrome 



