CONGRUITY OF THE EVIDENCE 289 



more complex. In referring to that most complex form of matter, 

 known as protoplasm, any analogous isomeric transformations 

 are no longer referred to even as possible. The matter itself 

 is admitted to be of the most changeable kind, and the forms 

 of living things are admitted to depend upon the intimate con- 

 stitution of the units of living matter from which they arise (the 

 ' physiological units ' of Spencer, or the ' ids ' of Weismann), and 

 yet not one word is said as to the existence among simple 

 organisms of transformations of form akin to those which we 

 know as occurring in such simple substances as carbon, phos- 

 phorus, salts of mercury and other metals, as well as in the 

 carbon compounds, as a result of isomeric changes. 



The writer, however, believes that analogous transformations of 

 living matter are constantly occurring among lower forms of animal 

 and vegetal life, and that these are, in part, represented by mul- 

 titudinous heterogenetic transformations, some few of which have 

 been studied in this work. 



These lower forms of life, for the most part, multiply, as I have 

 said, by mere ' discontinuous growth,' and their forms, like those 

 of crystals, seem absolutely dependent upon their molecular 

 constitution and the environing conditions in the midst of which 

 they exist. Changes of this or that kind in their environing 

 conditions, will, in many of them, lead to remarkable changes, 

 owing to alterations thereby induced in their molecular con- 

 stitution — alterations which have as their result the establishment 

 of new formative tendencies. Moreover, I believe that many of 

 the discrepant observations made by good observers as to the 

 ordinary phases in the life-history of such pleomorphic species as 

 Chlamydococcus, Pleurococcus, and many others, have been due 

 to modifications occurring from time to time in their developmental 

 phases, under the influence of special conditions of one or another 

 kind, though either of such phases may ultimately revert to the 

 form from which it started. The accounts that have been given 

 by good observers show that a regular order is not observed, and 

 that strange phases are, from time to time, apt to be intercalated. 

 Many of these lower forms of life are so much the creatures of 

 circumstances— so transitory in their duration — that I long ago 

 proposed to speak of them as ' Ephemeromorphs,' ' in contradis- 

 tinction to the regularly recurring forms comprised under, and 

 understood by, the term 'species.' 



' "The Beginnings of Life," 1872, vol. ii., p. 559. 

 19 



