212 THE MENDEL JOURNAL 



evolved by Natural selection operating through the medium of 

 spontaneous germinal variations. Those plants which have 

 mutated in the direction of acquiring this plasticity can live under 

 diverse conditions, because they can respond to them ; those 

 which have not thus acquired it, like the woodruff and the flax, 

 can only live under certain limited environments, because they 

 cannot respond to wider changes in their surroundings. 



In one part of his book, Professor Henslow asks us for the 

 evidence of elimination of the unfit. He asserts " that Nature 

 does not produce seedling plnats possessing structural and func- 

 tional defects." We have not far to go to find it. Any seed of 

 Pinus will provide it. In this seed, at a certain stage of develop- 

 ment, there are from sixteen to twenty embryos. At the germin- 

 ation of the seed only one comes forth as a seedling. The others 

 have been eliminated ; their metabolism fell behind the pace set by 

 the victor, they were unfit, and they perished. Such illustrations 

 can be multiplied and can be culled from the Animal Kingdom too. 



Those who are interested in these problems should of course 

 read the case for both sides. And, from the botanical standpoint 

 of the transmission of acquired characters, the reader cannot do 

 better than to carefully consider the facts described by Professor 

 Henslow in his book. 



The Causation of Sex.— % E. Ramley Dawson, L.R.C.P., 

 Lond., M.R.C.S., England. H. K. Lewis, London; 6s. 

 net, pp. XIL + 196. 



The problem of Sex has ever been one of the most fascinating 

 of biological problems. It has attracted to itself the attention of 

 both eminent zoologists and botanists, in this and other countries, 

 during the current and in past centuries. Around the relatively 

 few facts known concerning it, many hypotheses — too often 

 incorrectly called theories — have been woven. There are so 

 many of these that at the beginning of the last century it was 

 calculated more than five hundred of them had been framed 

 at one time or another. In the face of such an army of 

 hypotheses, one feels that Dr. Rumley Dawson's claim to have 

 framed a new one is courageous indeed. It is certain" that it 

 departs from the great majority of the older hypotheses Jn that 

 it excludes the influence of environmental factors in determining 

 Sex, and falls back wholly upon the inherent structure of the right 

 and left ovaries of the female. 



