94 



ADAPTATION AND DISEASE 



be attained by a short cut, there certain phases of the phylogeny 

 fail to be recapitulated. In short, the development of any 

 particular tissue may aptly be compared with the synthesis of 

 one of the higher organic compounds. That cannot be accom- 

 plished by taking so much Carbon, Hydrogen, Nitrogen, etc., 

 mixing and heating them together, but demands a long process 

 of building up — it may be a score or more successive processes 

 of combinations, associations and dissociations — before the final 

 product is attained ; the constant endeavour of the chemist 

 being to simplify the process, to arrive at the same results by 

 finding some reaction which will cut out half a dozen or more 

 of the steps and lead more rapidly and more economically to 

 the same result. 



(vii.) Amphimixis. — This mention of the contribution of the 

 two parental germ plasms to the fertilized germ cell, or zygote, 



Fig. 12. — A, biophore of paternal, B, biophore of maternal origin ; 1, 2, and 3, 

 various allelomorphic side-chains ; 4, side-chains common to both orders of 

 biophores. 



leads to certain important considerations. If the metabolic 

 activities of the cell are of the order here stated, and if, as is 

 evident from the studies of cytologists and embryologists, 

 equivalent amounts of heritable material — or biophores from 

 the two parents — reach the zygote and, in the subsequent process 

 of active cell division of the embryo, are contributed to each 



