LIXNEAX SOCIETT OF LOXDOX. 95 



out than ordinary Meudelian experiments, and require an 

 immensely longer time in order to obtain a definite result. 



[Dr. Lotsy talks airily of the advantage which iiis theory enjoys 

 of enabling us to dispense with intermediate links connecting 

 distinct phyla, and even suggests that the vertebrate skeleton may 

 have sprung into existence at once like Minei-va from the head of 

 Jove, owing to the bringing together of several factors by sexual 

 union. In answer to this, it may be stated that in those cases 

 M'here tlie palaeontological record is at all well preserved, as it 

 is in the case of the evolution of the bony elements of the 

 Aertebiate skeleton, there is no evidence of the sudden appearance 

 of new characters, but increasing evidence of evolution by slow 

 and gradual change.] 



Professor F. E. AVeiss, stated that, while agreeing with Dr. Lotsy 

 that in some genei-a, like Hosa and 11 nhtis, which ha\e a very large 

 number of species, some of these may have resulted from crossing; 

 yet in other cases where hybridization takes place no great variety 

 of forms has resulted under natural conditions. He continued: — 



I have been engaged for some years in an investigation of the 

 hybrid between Gtum urhanum and G. rivale, which is not infre- 

 quently found in Britain, and is often included in our Floras as 

 Getmi intermedium. I can fully corroborate Dr. Lotsy's observa- 

 tions as regards the segregation of species-hybrids in the F^ 

 generation. As already recorded bj^ me at the Dundee Meeting 

 of the Britisb Association, the F, generation of Geum tirharaim 

 xG. rivale is very varied, some of the forms being quite distinct 

 from either of the parents. Tet in nature these forms are very 

 rarely met with, tbongh the first hybrid is comparatively common 

 and very fertile. The comparative absence of the multifarious 

 segregates of Gexim inteiineclium (so-called) must, I think, be due 

 to the fact that it is more frequently fei-tilized by pollen from 

 one or other of the parental forms — the result being, as I have 

 found by experiment, a form resembling the parental species more 

 closely than the hybrid. It is probable that in nature, by such 

 crossing with the parent forms, the segregates of the hybrid tend 

 to disappear. This must, I think, be commonly the case Avitb 

 hybrids in the case of genera adapted to cross-pollination. 



AVitb regard to the restriction of the term species for geno- 

 typic forms, it seems to me, we should never be certain whether 

 plants, morphologically identical, belonged to the same species. 

 Physiologically they might be diverse. This would, for instance, 

 be the case with Cardamine pratensis and other self-sterile plants, 

 where individuals only are genotypes, and conseqiiently all the 

 offspring are physiologically heterozygotes. Dr. Lotsy recognized 

 this ditiiculty in speaking of Linaria. 



Major C. C. Hurst said : We are much obliged to Dr. Lotsy 

 for bringing forward this interesting question in such an able 



