220 THE INDUCTIONS OF BIOLOGY. 



cells. It seems obvious that this mysterious power "v^liich 

 they display, of originating a new and complex organism, 

 distinguishes them in the broadest way from portions of organic 

 substance in general. Nevertheless, the more we study the 

 evidence, the more is this assumption shaken— the more are 

 we led towards the conclusion, that these cells have not 

 been made by some unusual elaboration, fundamentally 

 different from all other cells. The first fact which 



points to this modified conclusion, is the fact recently dwelt 

 upon (§ 63), that in many plants and inferior animals, a 

 small fragment of tissue that is but little differentiated, is 

 capable of developing into the form of the organism from 

 which it was taken. Conclusive proof obliged us to admit, 

 that the component units of organisms, have inherent powers 

 of arranging themselves into the forms of the organisms to 

 which they belong. And if to these component units, which 

 we distinguished as physiological, such powers must be con- 

 ceded — if, under fit conditions, and when not much specialized, 

 they manifest such powers in a way as marked as that in 

 which the contents of sperm-cells and germ-cells manifest 

 them; then, it becomes clear that the properties of sperm- 

 cells and germ-cells are not so peculiar as we are apt to 

 assume. Again, the organs for preparing sperm- 



cells and germ-cells, have none of the speciality of struc- 

 ture which might be looked for, did sperm-cells and germ- 

 cells need endowing with properties essentially unlike 

 those of all other organic agents. On the contrary, these 

 reproductive centres proceed from tissues that are character- 

 ized by their low organization. In plants, for example, it is 

 not appendages that have acquired considerable structure, 

 which produce the fructifying particles : these arise at the 

 extremities of the axes, where the degree of structure is the 

 least. The embryo-cells are formed in the undifferentiated 

 part of the cambium-layer ; the pollen-grains are formed at 

 the little-differentiated extremities of the stamens ; and both 

 are homologous with simpl® epithelium-cells. Among many 



