94 



THE OCEAN WORLD. 



generally an oblique direction backwards, often terminating in a 

 great undivided stomach. 



The reproduction of the Infusoria exhibits some very surprising 

 phenomena, while it offers another proof of the wonderful means 

 Nature employs for perpetuating the races of animals. They can be 

 reproduced by three different processes : i. By gemmation, or bud- 

 ding, somewhat after the manner of plants. 2. By the spontaneous 

 division of the animal into two individuals a process known to 

 zoologists as fission. 3. By sexual reproduction ; for in these little 

 creatures it has recently been discovered that sexual differences exist. 



Fig. 27. Propagation of an Infusorian by spontaneous division. 



The singular phenomenon of spontaneous division may be wit- 

 nessed by any one having patience to examine the creature long 

 enough, isolated from its innumerable companions, under the micro- 

 scope. The oblong body of the animal may be observed to contract 

 at the middle, the compression becoming more and more marked. 

 The lower segment soon begins to show at the place of construction 

 a few vibratile cilia, thus indicating the place which will soon be a 

 new mouth ; this organ soon becomes more and more distinct, and 

 now the Infusorian literally divides itself into two parts. The two 

 halves separate from each other very quickly, each moiety having a 

 perfect resemblance to the form which gave them origin, and both 

 swim about with all the activity of perfect life. This process is 

 represented in Fig. 27, A and B being the adult, c the same in course 



