. The evolution and function of living purposive matter . ker-upof unconsidered trifles, guided by a decided preferencefor things useful to itself. Therefore, the tinyanimal manifests discrimina-tion, imperfect no doubt, butclearly recognisable. Andthe choice is beneficial,it contains an element ofpurpose. ^ In the year 1878, Pro-fessor Strasburger describedthe movements made by thezoospores (motile spores) ofUlothrix (Fig. 19), and otheralgfe, and showed that theirpower of locomotion resultedfrom various external forcesacting on their irritable livingprotoplasm. Professor J. Loeb holds that m
. The evolution and function of living purposive matter . ker-upof unconsidered trifles, guided by a decided preferencefor things useful to itself. Therefore, the tinyanimal manifests discrimina-tion, imperfect no doubt, butclearly recognisable. Andthe choice is beneficial,it contains an element ofpurpose. ^ In the year 1878, Pro-fessor Strasburger describedthe movements made by thezoospores (motile spores) ofUlothrix (Fig. 19), and otheralgfe, and showed that theirpower of locomotion resultedfrom various external forcesacting on their irritable livingprotoplasm. Professor J. Loeb holds that movements such asthose to which we have referred in the lower algse, notonly occur in animal organisms but are referable tothe same causes or tropisms. He believes thesemovements depend, first, upon the specific irritabilityof certain elements of the body surface, and secondly,upon the relations of symmetry of the body. Inhis opinion symmetrical elements at the surface of 1 The Physical Basis of Life, by W B. Hardy, Science Progress,October 1906, p. Fio. 19.—B, Fully developedspore of Ulothrix a, small sporenlth two clUa; &, small sporesuniting to form a fertile beioff. 164 MECHANICAL MOVEMENTS the body have the same irritability, unsymmetricalelements have a different irritability. Those nearerthe oral pole or anterior end of a being possess anirritability greater than that of those near the oppositepole. These conditions force an animal to placeitself towards a source of stimulation or away from Loeb rightly maintains that these move-ments in the lower forms of plants and animals areidentical in their nature, as we assume, because thefundamental properties possessed by animal andvegetable protoplasm are identical, both having in allprobability arisen out- of a common simpler ancestralstock. Professor Loeb, in order to illustrate the principlehe advocates, refers to the movements of a moth in thepresence of a lighted lamp. He states that if theinsect be str
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