INTRODUCTORY 1 1 



the ages so far dominant as to entirely obscure less progressive 

 types ? The Myxomycetes are independent ; all that we may 

 attempt is to assert their nearer kinship with one or other of 

 Life's great branches. 



The cellulose of the Slime-mould looks toward the world 

 of plants. The aerial fructification and stipitate habit of the 

 higher forms tends in the same direction. The disposition to 

 attach themselves to some fixed base is a curious characteristic 

 of plants, more pronounced as we ascend the scale ; but by no 

 means lacking in many of the simplest, Diatoms, filamentous 

 Algse, etc., and it is quite as reasonable to call a Vorticella or 

 Stentor, by virtue of his stipitate form and habit, a plant as to 

 call a Slime-mould an animal because in one stage of its 

 history it resembles an amoeba. The whole life of the organ- 

 ism in any case must be taken into account. At the outset 

 plants and animals are alike ; there is no doubt about it ; they 

 differ in the course of their life histories. The plasmodium 

 is the vegetative phase of the Slime-mould. It needs no cell- 

 walls of cellulose, no more than do the dividing cells of a 

 lily-endosperm ; both are nourished by organic food and resort 

 to walls only as conditions change. The possession of walls 

 is an indication of some maturity. In the Slime-mould the 

 assumption of walls is indeed delayed, but merely delayed. 

 Walls at length appear, and when they do come they are like 

 those of the lily ; they are cellulose. The Myxomycetes may 

 be regarded as a section of the organic world in which the 

 forces of heredity are at a maximum, whatever those forces 

 may be. Slime-moulds have in smallest degree responded to 

 the stimulus of environment. They have, it is true, escaped 

 the sea, the fresh waters in part, and become adapted to hab- 

 itation on dry land ; but nothing more. It is instructive to 

 reflect that even in her most highly differentiated forms the 

 channel which Nature elects for the transmissal of that hered- 

 ity may bestow, is naught else than a minute mass of naked 

 protoplasm. Nature reverts, we say, to her most ancient and 

 simple p'hases, and heredity is still consonant with simplicity. 



