294 STUDIES IN THE EVOLUTION OF ANIMALS 



admitted that Goats and Sheep, Rabbits and Hares, common 

 Fowls and Pheasants, Pheasants of different species, Tigers and 

 Lions, 1 Zebras, Asses and Horses do interbreed, and several of them 

 produce fertile hybrids. The question is What is a species ? 



What possible influence in ancient times could have caused a 

 disturbance in the development of ova so as to evolve abnormal 

 forms, say in fishes, as evidenced by the vast number of new types 

 linked by some characters, and yet unlinked by others, with their 

 forerunners. Several causes suggest themselves, viz. : 



(a) Submarine volcanoes heating the water and diffusing new 

 chemical compounds dissolved in it. 



(U) Shakings and concussions of the water and of the sea bottom. 



(c) Electrical discharges connected with submarine volcanic 

 explosions, and so forth. 



I shall now discuss some human monstrosities to see how far 

 such a notion as I have foreshadowed in the foregoing lines has 

 any basis in fact. 



Cases of supernumerary digits in Man are by no means rare. 

 Darwin 2 states that ' Dr. Burt Wilder 3 has tabulated the cases of 

 152 individuals with supernumerary digits, of which 86 were males, 

 and 39, or less than half, females ; the remaining 27 being of un- 

 known sex ' 



Then 4 he says that * supernumerary fingers and toes are emin- 

 ently liable, as various authors have insisted, to be inherited. Poly- 

 dactylism graduates by multifarious steps, from a mere cutaneous 

 appendage, not including any bone, to a double hand. But (p. 458) 

 an additional digit, supported on a metacarpal bone, and furnished 

 with all the proper muscles, nerves, and vessels, is sometimes so 



1 See Nature of 27th April 1893, p. 607, on Lion-Tiger hybrids. 



2 Descent of Man, p. 223. 



3 Massachusetts Medical Society, vol. ii., No. 3. 1868, p. 9. 



4 Animals and Plants under Domestication, vol. i. p. 457. 



