88 'WHAT IS A SPECIES?' 



has been already pointed out on p. 65 that, should 

 preferential Syngamy be established on a large scale, the 

 instincts concerned would assume fundamental significance 

 in the origin of species. 



Asyngamy as a consequence of the breaking of 

 a Syngamic Chain. 



It is also possible that Asyngamy may be brought about 

 by the breaking of what we may call ' a Syngamic Chain'. 

 In the case of large and widely-distributed interbreed- 

 ing communities it is an open question whether Syngamy 

 would freely take place between the most distant of the 

 outlying sections if directly brought into contact, and 

 whether, even if Syngamy prevailed, there would be any 

 diminution in fertility. 



Limnas chrysippus, perhaps the commonest butterfly 

 in the world, forms a probably continuous syngamic chain 

 stretching from the Cape of Good Hope at least as far as 

 Southern China. It is even reported from Japan. The 

 far Eastern forms are readily distinguishable by the 

 greater size of a single white spot, giving quite a different 

 appearance to the fore-wing. If pupae or eggs were 

 transferred from Hong-Kong or Macao to South Africa, 

 would the perfect butterflies freely interbreed with the 

 indigenous forms of chrysippus ? We do not know ; but 

 it is an experiment well worth trying, and one which 



' I saw some broods of P. phlaeas lately that differed from each other, 

 but each brood was remarkably uniform. There were three broods, all bred 

 in the same conditions, in a greenhouse (by Mr. Carpenter of Leatherhead). 

 It seems difficult to explain this, unless both parents of each brood were 

 very nearly identical. 



' Mr. Frohawk, who has bred the species largely, tells me he has noticed 

 similar facts. 



'When I bred Acronycta Iridens and psi largely, some fifteen or more 

 years ago, I noticed that each brood had its own facies, and suggested 

 that tridens was now trying to break up into separate species just as some 

 ancestor split into psi, tridens, and cuspis, 



' Another fact I observed in Acronycta rather bears on the other side 

 of the question. Of A. slrigosa I reared a large brood, which paired 

 readily and frequently together, but no eggs were laid. I then got some 

 captured males, which paired with equal readiness with the bred females, 

 and as a result obtained plenty of fertile eggs.' 



