Nature of Heredity. 331 



all other parts, and cannot be changed without initiating changes in 

 all other parts — if the limit of change is the establishment of a com- 

 plete harmonv among the movements, molecular and other, of all 

 parts; then among other parts that are modified, molecularly or 

 othenvise, must be those which cast off the germs of new organisms. 

 The molecules of their produced germs must tend ever to conform 

 the motions of their components, and, therefore, the arrangements 

 of their components, to the molecular forces of the organism as a 

 whole: and if this aggregate of molecular forces is modified in its 

 distribution by a local change of structure, the molecules of the 

 germs must be gradually changed in the motions and arrangements 

 of their components, until they are readjusted to the aggregate of 

 molecular forces. For to hold that the moving equilibrium of an 

 organism may be altered without altering the movements going on 

 in a particular part of it is to hold that these movements will not be 

 affected by the altered distribution of forces ; and to hold this is to 

 deny the persistence of force.'"* 



We may readily admit with Weismann and his school the con- 

 tinuity of the germ-plasm from generation to generation, and we 

 certainly grant the immense importance of the chromosomes in 

 heredity, but still there appears to be no valid reason vet brought 

 forward for denying the influence of the body upon the germ-cells, 

 although this influence may require a long period of time to make 

 itself felt. Nor is there any reason for supposing, with Darwin, that 

 a migration of material particles is necessary in order to ensul-e that 

 the germ-cells shall be able to reproduce the body in all its details 

 in the process of development. 



In the inorganic world the recently discovered phenomena of 

 wireless telegraphy shew clearly enough how complex forces may be 

 transmitted from one centre to another at a distance without any 

 material connection, and it is not difficult to shew that a living cell 

 may influence another at a distance without either organic connection 

 or the transfer of material particles. 



A good illustration of this transference of stimuli from one cell 

 to another at a distance is afforded by the fresh-water alga Spirog\ra\, 

 This little plant occurs in the form of tangled masses of slender 

 green threads, each thread being composed of a single row of cvlin- 

 drical cells placed end to end, and each cell being enclosed in a firm 

 wall of transparent cellulo.se. At certain times a process of sexual 

 reproduction takes place, commencing with a conjugation between 

 the cells of two filaments which happen to be lying side by side and 

 parallel with one another. One of these filaments mav be regarded 

 as male and the other as female, and the process appears to be 

 inaugurated by the cells of the male filament. Each of these which 

 happens to have a cell in the other filament opposite to it puts forth 



" Principles of Biology, Vol, II., p. 387. 



t Attention has already been called to this case, c.ii,., by Professor H. B. Orr, 

 in his interesting- and suggestive work on " Development and Heredity " ; but I 

 am not aware that anyone has hitherto demonstrated the inadequacy of the 

 chemiotactic theory wliich has been adduced in explanation of the facts." 



