THE FUNCTIONS OF THE ORGANISM 15 



kind. In the interior of each individual certain 

 special organs occur, in one individual an organ 

 producing ova, in another an organ producing sperms. 

 Sperms and ova are emitted from the male and 

 female frogs respectively, and after the fusion of 

 ovum and sperm, the product or oosperm passes 

 through certain intermediate stages, and in time 

 develops into a new frog. In the life-history of this 

 animal there is no evi- 

 dence of an asexual method 

 of reproduction, such as 

 has been noted as occur- 

 ring in Vaucheria. 



The feeble, but still 

 observable, sensitivity to 

 external influences which 

 we recognised in Vaucheria 

 is much more clearly 

 exhibited by the frog. 

 Not only is the general 

 body sensitive to extremes 

 of heat and cold and other 

 climatic influences, but 

 there are also specific 



FIG. 8. D, ovum ; A, B, C, 

 early stages in embryology; 

 E, sperm of frog. 



eyes for receiving light 

 sound impulses, special 



organs developed for the 

 express purpose of re- 

 ceiving special impulses ; 

 impulses, ears to receive 



tactile organs in the skin for the reception of contact 

 impulses, taste organs in the mouth and adjacent 

 cavity for the appreciation of food, and so on. More- 

 over, we find a special system of conducting strands 

 nerves having for their duty the transmission of 

 impulses to a central organ, the brain, from which 

 again another set of nerves transmit impulses gene- 



