MIMIC BY. 349 



nature, a great check to increase is to be found in the difficulty 

 the seeds experience in finding a proper soil in which to germi- 

 nate, as well as in other sources of destruction. 



The advantages of, or the part played by fecundity in the 

 preservation of many species is evidently of the most complete 

 and far-reaching character. This seems particularly and more 

 frequently the case with fishes, * the reasons for which are not 

 difficult to comprehend. It has been urged that the pale colour 

 of the under side of fishes makes it more difficult for enemies to 

 detect them from beneath ; but this is probably a truism without 

 denoting any evolved protection, and may be due to other causes. 

 The survival is probably owing to fecundity alone, which prevents 

 extermination from the many foes and adverse conditions which 

 environ their lives. One may stand before the tank in a large 

 aquarium, and be impressed with the assimilative colouration of 

 the upper sides of flat-fishes to the sandy or pebbly bottom on 

 which they rest, but still no difficulty is experienced in dis- 

 tinguishing the living creatures ; and if this be so, and with our 

 untrained perceptions, how much stronger must be the detective 

 powers of those natural enemies whose prey is their necessity ! 

 The 1.30,000 eggs said to be carried by a Sole of one pound weight 

 is probably the factor which prevents annihilation, and not a 

 moderate disguise which, without deceiving ourselves, is still less 

 likely to mislead enemies whose lives depend on its destruction. 

 Nature is here quite " careless of the single life," but, by fecundity, 

 " so careful of the type." In our oceans and rivers the course 

 of evolution has decided that the most prolific shall survive, and 

 this is probably with fish the great factor of protection. Here 

 individuality is lost, and Providence is with the big battalions. 



* Of course it is not suggested that all fish survive through fecundity 

 alone. The European Goby (Latrunculus pellucidus) and the Sea- Stickle- 

 back (Gastrosteus spinachia) have apparently been proved to die within a 

 year of their birth. In these cases other protection seems to be afforded. 

 According to Dr. Giinther, the fish spawns in June and July. In April the 

 males lose the small teeth, which are replaced by very long and strong teeth, 

 the jaws themselves being stronger. The teeth of the females remain un- 

 changed. In July and August all the adults die off (' Introd. Study Fishes,' 

 p. 487). In this case the male may defend the progeny. G. spinachia is, 

 on the same authority, a " nest builder, choosing for its operations especially 

 the shallows of brackish water which are covered with Zostera" {ibid. p. 507). 



