368 SCIENCE PROGRESS 



have a double action in inducing the development of the egg. Professor Loeb 

 and the other investigators whose results he correlates with his own, have gone 

 a long way towards establishing the nature of these processes. First of all the 

 so-called fertilisation or vitelline membrane is formed. This was long thought 

 to be a phenomenon of minor importance, but has now been proved to be a 

 necessary part of the process. Various artificial agents, monobasic acids, 

 glucosides, soaps, lysins, and serums, introduced into the egg in certain cases, 

 allowed to diffuse into it in the more common cases, induce the formation of 

 the membrane. This having been formed, the eggs proceed to segment, but, 

 except in rare instances, the segmentation is speedily replaced by cytolosis. The 

 egg and its contents break down and die. The action of these agents is not 

 specific, and Professor Loeb thinks that their effect is to overthrow the stability 

 of the emulsions of which the surface of the egg is composed, and in fact is a first 

 stage in the cytolitic death of the contents. 



The formation of the membrane appears to lead to segmentation chiefly by 

 accelerating the process of oxidation, and in fact transforming the egg from 

 being anaerobic to being asrobic. Complete removal of oxygen from the medium 

 containing the eggs arrests any further development whether in the case of 

 normal fertilisation, natural or artificial parthenogenesis. 



The second factor is an agent which arrests the normal cytolysis and allows 

 the eggs after the formation of the membrane to proceed to full development. 

 In artificial fertilisation, the second factor also is not specific, but the result is 

 produced almost by any hypertonic agent, that is to say any agent which raises 

 the concentration of the water, salt or sugar being used successfully. Loeb has 

 found that the hypertonic treatment is effective even if it is applied before the 

 formation of the membrane. 



We have given a very short summary of Loeb's more important results. In 

 the volume before us they are set forth with full detail and there are important 

 discussions of the various chemical details involved. From a general point of 

 view, Loeb's work falls in with advances in knowledge of the chemistry of 

 proteids, leading towards knowledge of the constitution of protoplasm, and with 

 the work of Biitschli and others on the structure of protoplasm. It may be the 

 case that even when all the chemical and physical process of living matter have 

 been tracked out and understood, there may remain something different from 

 chemical and physical action, something that is peculiar to life and not to be 

 resolved into inorganic agents. But the fact remains that step by step inorganic 

 forces and agencies are being proved to explain a greater and greater amount of 

 vital action. 



Controlled Natural Selection and Value Marking. By J. C. Mottram, M.B. 

 [Pp. vii + 130.] (London: Longmans, Green & Co., 1914. Price 3s. 6d. 

 net.) 



Mr. MOTTRAM has propounded an interesting theory with lucidity and succinct- 

 ness, and the fashion in which he offers it as a working hypothesis to be tested 

 by observation, rather than as a complete solution, is attractive and scientific. 

 Every one knows that Darwin's theory of sexual selection presents many difficulties 

 and is far from having convinced either those who stood in the forefront of the 

 battle for natural selection or the general body of later naturalists. The view that 

 the exuberances of sexual habit, structure, and coloration are the mere efflorescence 

 of exalted vitality, and the Mendelian attempts to associate them with the presence 

 or absence of factors unevenly distributed in inheritance do not satisfy our craving 



