If we now ask why and by what mysterious law all these exact and elaborate choric movements take place Weismann and his school refer us to “chemotactic forces,” the nature of which is yet unknown. Chemotaxis means simply the effect of the _presence_ of certain substances on vital organisms without specific chemical action. The really essential fact is that these special chemotactic forces are working _in living protoplasm_. Life is not the product or the slave of any chemotactic forces, but their maker and steersman. The following passage from a work of the late Prof. Geo. Rolleston may be pertinently quoted here:— “There exists, as is well known, a tendency to resolve all physiological into physico-chemical phenomena: undoubtedly many have been, and some more may still remain to be, so resolved; but the public may rest assured that in the kingdom of Biology no desire for a rectification of frontiers will ever be called out by any such attempts at, or successes in the way of, encroachment; and that where physics and chemistry can show that physico-chemical agencies are sufficient to account for the phenomena, there their claim upon the territory will be acceded to, as in the cases we have been glancing at [certain animal poisons], and where such claims cannot be established and fail to come up to the quantitative requirements of strict science, as in the cases of continuous and of discontinuous development or self-multiplication of a contagious germ, and in some others, they will be disallowed.”[45] This was written in 1870. A generation later the attempt to reduce life to a physico-chemical phenomenon had not made much way, as may be judged by the following passage from Strasburger’s Text Book of Botany:—[46] “Vital phenomena are essentially bound up with the living protoplasm. No other substance exhibits a similar series of remarkable and varied phenomena, such as we may compare with the attributes of life. As both physics and chemistry have been restricted to the investigation of lifeless bodies, any attempt to explain vital phenomena solely by chemical and physical laws could only be induced by a false conception of their real significance, and must lead to fruitless results. The physical attributes of air, water, and of the glasses and metals made use of in physical apparatus, can never explain qualities like nutrition, respiration, growth, irritability and reproduction.” And Wilson concludes his work by the admission that “the study of the cell has on the whole seemed to widen rather than to narrow the enormous gap that separates even the lowest forms of life from the inorganic world.”[47] “The lowest _observed_ forms of life” would have been a more exact way of stating the fact.