470 Reports & Proceedings — British Association. 



is thick, the heat-gradient low, and there has been no folding since remote 

 times. Magmas appear to have reached surface by fault fissures from 

 great depths where high pressures are associated with comparatively low 

 temperatures. Crystallization proceeding under such circumstances, 

 there would be an early formation of minerals with small molecular volumes, 

 garnet, kyanite, epidote, and zoisite, minerals rich in lime and alumina. 

 Zoisite may be regarded as high pressure representative of anorthite, but 

 there is no corresponding representative of albite or orthoclase. Con- 

 sequently we should expect a residual magma exceptionally rich in alkalies 

 which would furnish material necessary for formation of alkali rocks. 



4. Reports of Research Committees. 



5. Joint meeting with Sections D and K. Discussion: Mendelism 

 and Palaeontology : The Factorial Interpretation of Gradual 

 Changes, especially when New Characters appear late in the 

 Individual Life-cycle. Dr. F. A. Bather, F.R.S. 



The question posed. Can characters be regarded as independent, i.e. 

 as manifestations of independent factors in the germ ? Does evolution 

 take place solely by addition or loss of such factors ? Is there not also 

 a gradtxal modification of the body, resulting in a continuous transition ? 

 Palaeontologists find such transition to be the rule in those cases where the 

 geological record is sufficiently complete. (See President's Address, 

 Section C, heading "Continuity in Development".) Palaeontologists 

 support the theory of recapitulation, and believe that in many cases 

 gradual modification of the adult and senile body is, in the course 

 of race-history, pushed back to earlier growth stages. (See President's 

 Address, Section C, heading " Recapitulation ".) Can such cases be 

 explained by independent factors in the germ ? Does not that 

 hypothesis involve, first, an alteration of the germ through change in the 

 body, secondly the determination of that germinal change in a direction 

 harmonious with bodily change ? 



Dr. R. RuGGLES Gates : — 



According to mutationist hypothesis, germinal characters arise as 

 alterations of single elements of the germ plasm. This conception 

 avoids the difficulties involved in considering the change as due to 

 the loss or addition of a factor. It recognizes on the one hand the 

 solidarity of the germ plasm as a whole, and on the other the 

 indepsndent origin of variations in Its several parts. Such variations 

 are termed karyogenetic, since they apparently arise in the nuclei 

 and are perpetuated by miotic division. Mutations of this nature 

 are almost universal amongst wild plants and animals, and sorne of 

 them are so small that for general purposes they are practically 

 continuous. They differ from the Darwinian conception of continuous 

 variation, however, in that (i) they do not arise in any regular order, (ii) 

 they are inherited as separate units. But recapitulation is an almost 

 equally widespread phenomenon in animals, and to a less extent in plants. 

 The recapitulation in animal embryos, and in such fossil groups as the 

 Ammonites, implies the addition of terminal stages to the development 

 of the organism. From the standpoint of organic structure this process 

 is clearly different from a mutation by which the nuclear unit is modified 

 throughout the organism. Recapitulatory characters thus fall into two 

 groups : (i) embryonic, which appear always to imjDly adaptation of the 

 organism to different conditions, and are best explained by the neo- 

 Lamarckian principle ; (ii) orthogenetic, which appear late in the life- 

 cycle but are germinal in origin and non-adaptional. 



Professor J. E. Duerden : Mendelism ; Palaeontology ; 

 Evolution. 



