These experiments were continued and amplified by Shibata. Bruchmann[83] found that the spermatozoa of _Lycopodium_ are positively chemotactic to citric acid and salts of this acid, although no citric acid could be shown in the contents of the archegonia. They are also positively chemotactic to the watery extract from archegonia. [83] Bruchmann, H., _Flora_, 1909, ic., 193. Dewitz, Buller, and the writer have vainly tried to prove the existence of a positive chemotropism of spermatozoa to eggs of the same species. Lillie claims to have proved a positive chemotropism of the sperm of sea urchins to “fertilizin,” but such a conclusion is only justified if a method similar to that of Pfeffer’s with capillary tubes, gives positive results; such a method was not used in Lillie’s experiments. It seems that the fertilization of the egg by sperm is rendered possible by two facts; first that where fertilization takes place outside the body egg and sperm are shed simultaneously by the two sexes. This can be easily observed in the case of fish. But it is also the case in invertebrates. Thus the writer has observed that the sea urchins _Strongylocentrotus purpuratus_ at the shore of Pacific Grove all spawn simultaneously. The examination extended over several miles of shore. At such spawning seasons the sea water becomes a suspension of sperm. The second fact guaranteeing the fertilization of the eggs is the overwhelming excess of spermatozoa over eggs. The enormous waste in animated nature is in agreement with the idea of a lack of purpose; since in this case the laws of chance must play a great rôle; and the origin of durable organisms by laws of chance is only comprehensible on the basis of an enormous wastefulness, for which evidence is not lacking. CHAPTER V ARTIFICIAL PARTHENOGENESIS