gS PROCEEDIXGS OF THE LIXXEAX SOCIETY. 



The study of the geographical races of animals pointed to the 

 same conclusion. When two of these races met and interbred, as 

 happened in Africa — where eastern and western forms came 

 together at the Victoria Nyanza or the Great Eift A'alle}', — we 

 ought to find, according to Dr. Lotsy's hyporhesis, variation 

 radiating in many directions. What we do find is either a 

 series of A'ariatious intermediate between each of the two inter- 

 mingling geographical races or else an abrupt replacement of the 

 one race by the other. In the latter examples, a Mendelian 

 interpretation was probable. 



Dr. LoxsT : — The divergence of opinion expressed shows how 

 little Ave really haow of evolution. We can imagine several ways 

 in which species can originate, but I think oue way only is really 

 knoivji to us, viz. by crossing. I have therefore tried to show 

 that a theory based on this fact is able to give a satisfactory 

 explanation of species-formation in general. Of course it does 

 not follow that this explanation is the right one, but I beg to call 

 vour attention to the fact that it is in agreement with t\\o funda- 

 mental facts discovered by Jordan, viz., the constancy of Jordanian 

 species, and the fact that the Linnean species is a kind of genus 

 composed of vast groups of Jordanian species growing socially 

 in nature. In this respect it is very satisfactory to me that 

 Dr. Eeudle thinks that the result of segregation following a cross 

 suggests tlie origin of genera rather than of species. 



The hour is too late for a detailed reply. I should like, how- 

 ever, to point out tliat I have limited my remarks to the origin of 

 species, and not treated the question what becomes of these in the 

 struggle for existence, etc. It seems to me that we must keep 

 these two important questions more strictly apart thai some of 

 the speakers have done. I shall be glad to try to meet Dr. Gates's 

 challenges as soon as he obtains similar cytological results by in- 

 vestigating an undoubtedly pure species, as he has obtained no^v 

 on material of very doubtful, probably of heterozygous nature. 

 Mr. Sutton's criticism has already been met above ; Beta maritima 

 is in nature already a mixture of several microspecies. To finish, 

 I would beg all who criticise my views to keep in mind that the 

 Linnean species is not a unit, but a mixture of heterogeneous 

 things, in which the Jordanian species are the most important. 



Doubtless opportunity will offer itself to answer the objections 

 made, more fully in some future paper. 



