MODES OF ORIGIN COMPARED 57 



Because in some solutions different forms of Bacteria invariably 

 reproduce their like, just as in other solutions Torulae reproduce 

 Torulas — because each of these forms 'breeds true' — they are 

 commonly regarded and named as so many distinct ' species.' 

 This, however, is far from being justifiable. A fragment which 

 detaches itself from one of the lowest living things has just as much 

 tendency to grow into the form of its parent, as the fragment 

 detached from a given crystal has to reproduce a similar crystalline 

 form. In each case, however, the parent form is reproduced only 

 so long as the conditions remain the same. Placed under new 

 conditions the crystalline fragment may grow up with a modified 

 form ; and, similarly, under the influence of new conditions, a 

 change may overtake a portion of matter thrown off from a pre- 

 existing living form. In order that the crystal may lapse into 

 another form, it seems necessary that the new conditions shall 

 be capable of bringing about a new molecular arrangement (or 

 isomeric state) of the ci-ystalline matter. And, similarly, new con- 

 ditions would probably change primordial living forms, only so 

 long as they were capable of inducing internal molecular re- 

 arrangements. It is, therefore, only to be expected that even 

 new-born organic forms should remain constant, or ' breed true ' 

 so long as we have to do with the same fluids under unaltered 

 conditions. 



But since it is well known that different kinds of Bacteria and 

 Torulae may frequently be seen to grow in the same solution, we 

 are compelled to believe that some minute difference in the con- 

 stitution of their ultimate units exists, and that each has the power 

 of causing, during its acts of growth, the synthesis of similar units 

 of living matter. The occurrence of one or the other form need 

 not, therefore, be always or wholly attributable to mere difference 

 of ' conditions ' — it ought to be mostly due to an actual, though 

 minute, difference in the molecular constitution of the initial units 

 of living matter. For although the same crystalline matter under 

 the influence of different conditions may assume different crystal- 

 line forms, it is much more common for different crystallisable 

 compounds to aggregate into different geometrical forms. 



It must, moreover, be quite familiar to all who have had much 

 experience in this particular line of research, that Torulee fre- 

 quently exist in abundance in certain solutions, and yet show 

 no signs of developing into Fungi. Discontinuous growth goes 

 on rather than continuous growth. So much is this the case, that 



