254 THE INDUCTIONS OF BIOLOGY. 



and for accepting the opposite supposition, that they are cells 

 differing from others rather in being unspecialized. And here 

 the assumption to which we seem driven by the ensemble of 

 the evidence, is, that sperm-cells and germ-cells are essentially 

 nothing more than vehicles, in which are contained small 

 groups of the physiological units in a fit state for obeying their 

 proclivity towards the structural arrangement of the species 

 (hey belong to. 



Thus the phenomena of Heredity are seen to assimilate 

 with other phenomena ; and the assumption which these 

 other phenomena thrust on us, appears to be equally 

 thrust on us by the phenomena of Heredity. * We must con- 

 clude that the likeness of any organism to either parent, is 

 conveyed by the special tendencies of the physiological units 

 derived from that parent. In the fertilized germ we have 

 two groups of physiological units, slightly different in their 

 structures. These slightly-different units, severally multiply 

 at the expense of the nutriment supplied to the unfolding germ 

 each kind moulding this nutriment into units of its own 

 type. Throughout the process of evolution, the two kinds of 

 units, mainly agreeing in their polarities and in the form 

 which they tend to build themselves into, but having mfuor 

 differences, work in unison to produce an organism of the 

 species from which they were derived, but work in antago asm 

 to produce copies of their respective parent- organisms. And 

 hence ultimately results, an organism in which traits o r the 

 one are mixed with traits of the other. 



If the likeness of offspring to parents is thus determined, it 

 becomes manifest, a priori, that besides the transmission of 

 generic and specific peculiarities, there will be a transmis- 

 sion of those individual peculiarities which, arising without 

 assignable causes, are classed as " spontaneous.'* For if the 

 assumption of a special arrangement or parts by an organism, 

 is due to the proclivity of its physiological units towards 

 that arrangement ; then the assumption of an arrangement 

 of parts slightly different from that of the species, implies 



