REPRODUCTION 



23 



but only when in close proximity, so that external union 

 is largely left to chance. It is only when we ascend higher 

 in the scale of organization that special precautions are 

 taken to insure the safe union of both sex-elements. Thus 

 the male cuttle-fish {Argonaiita) discharges one of his 

 modified arms filled with spermatophores (packets of 

 spermatozoa) bodily into the cavity of the female, where 

 it bursts. The female fish lay their eggs, closely followed 

 by the attracted males, who thereupon fertilize the eggs 

 with their sperm. A 

 further step in this 

 direction is made by 

 the frog. Here fertili- 

 zation is still outside 

 the body of the 

 mother - animal, but 

 the male, embracing 

 the female, liberates 

 the spermatozoa 

 directly on the eggs 

 as they are laid. Final 

 security is reached by 

 the act of copulation 

 proper, where nothing 

 is left to chance. 

 Special organs exist 



in the female to receive the sperm, in the male to 

 introduce it into the female sexual organs, where the 

 ovum is ready to unite with it in order to accomplish 

 the act of fertilization. 



Fig. 17. — Male of Cuttlefish (Ar- 

 gonauta) with modified Arm. 



{From Geddes and Thomson, " The 

 Evolution of Sex.") 



(h) Autogamy. 



While in Heterogamy we have the union of two distinct 

 individuals — that of a male with a female — in Autogamy 

 the organism, as it were, mates itself, both kinds of sex- 

 cells being present within the same individual. Such indi- 



