Even in an Amœba (Fig. 59) we might picture the process of inheritance as equally simple, though in so doing we should probably be making a fallacious inference, for the structure of these lowest unicellular animals probably seems to us simpler and more homogeneous than it really is. Among Infusorians it is quite obvious that inheritance implies more than the mere halving of the mother-animal into the two daughter-cells; something more must be involved. For among these unicellular animals the differentiation of the body is not only great, but it is unsymmetrical. The posterior and the anterior ends are different, and the transverse division of the animal, in which the process of reproduction here consists, does not produce two halves, but two very unequal portions. In the division of _Stentor_, the so-called trumpet-animalcule (Fig. 60), the anterior portion contains the funnel-shaped mouth and gullet with its complicated nutritive apparatus, the circular peristome with its spirally curved rows of composite ciliated plates, the so-called membranellæ, and so forth; the posterior half contains nothing of all this, but possesses the foot of the mother-Stentor with its attaching organ, which the anterior half lacks. But each of the two portions possesses the power of 'regeneration,' that is, it is able to develop anew the missing parts, mouth or foot, and so on. So that here there is no longer merely a simple continuance of the maternal organization in the daughter-animals, there is something new added, something which requires explanation; we are confronted with the first riddle of heredity. Simple growth does not explain the phenomenon, for what has to be added to complete the halved portions has a different structure, a different form, different accessory apparatus from any that the halves themselves possess. It in no way affects this state of matters that in the normal process of division in Infusorians the formation of the new mouth and peristome-region begins before the halves have actually separated, for even if a Stentor be cut in two artificially the cut halves form complete animals. And, indeed, a Stentor may be cut into three or four pieces, and in certain conditions each piece will develop into a complete animal. These pieces must therefore possess something more than the mere power of growth. We shall try later on to discover whether this marvellous invisible transmission of characters, this implication of the whole in each of the parts, can be in any way theoretically expressed and included in our scheme of conceptual formulation.