376 Geological Society: — 



to two forms or two systems of forms, might be called Inva- 

 rians Duplex, or Versicolor, or after the name of the person 

 who first imported the notion of contragredience into the 

 subject. 



A simple invariant may be likened to a monocotyledonous, 

 a contrariant to a dicotyledonous plant. And, again, an 

 assembly of forms containing a system of covariantive sets of 

 variables may be regarded as a monogamous, one containing 

 a system of sets partly covariantive and partly contravarian- 

 tive, as a digamous complex ; and in the latter case there will 

 be the further distinction into dioecious or monoecious ; for 

 the two kinds of systems of variables may be confined to sepa- 

 rate forms, or appear together in the same mixed form, or they 

 may occur together in some of the forms and separate in the 

 others. 



In order to illustrate the position that such kind of analogies 

 are not purely fanciful, but have their origin in the Unity of 

 Nature, alike in its intellectual and its physical manifestations, 

 let me be allowed to recall the instance that I was led a priori 

 by a somewhat similar parallelism to anticipate a biological 

 possibility, which my distinguished colleague Prof. Martin, 

 of the Johns Hopkins University, was good enough to point 

 out to me is an actual fact in nature connected with Darwin's 

 theory of superfluous males. See " Constructive Theory of 

 Partitions," American Journal of Mathematics, vol. vi. foot- 

 note to the Eosodion. 



New College, Oxford, 

 September 17, 1884. 



XLI. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from p. 229.] 



May 14, 1884.— Prof. T. G. Bonney, D.Sc, E.R.S., President, 

 in the Chair. 



THE following communications were read : — 

 1. " On the Pre-Cambrian Rocks of Pembrokeshire, with especial 

 reference to the St. David's District." By Dr. Henry Hicks, E.G.S., 

 with an Appendix by Thomas Davies, Esq., E.G.S. 



The author, in this paper, gave further detailed evidence in addition 

 to that already submitted by him, to show that the Geological Survey 

 Map of the district of St. David's and of other parts of Pembrokeshire 

 is incorrect in some of its most essential features, and inaccurate in 

 very many of its petrographical and stratigraphical details. Some 

 new areas in South Pembrokeshire were also referred to. He 



