224 THE PHYSIOLOGY OF REPRODUCTION 



strengthen and regenerate our home stock."'' The same result is 

 said to have been achieved in the descendants of British horses 

 (especially Hackneys) imported into Ai'gentina.^ 



The case of the Porto Santo rabbits and that .of the goats of Jiian 

 Fernandez, which are cited by Huth ^ as evidence that in-breeding is 

 harmless, may perhaps be similarly explained. 



Moreover, such an interpretation is not necessarily inconsistent 

 with the genetic explanation given by East and Jones (see above, 

 p. 218), according to whom the infertility may be due to adverse 

 factors in certain strains, since the environment may exercise an 

 effect on the germ-plasm through the body cells and so produce a 

 selective influence. 



It would seem on the whole that the only feature common to 

 conjugation or fertilisation throughbut the animal kingdom is 

 biparental inheritance. The association of fertilisation or conjugation 

 with reproduction is not an essential one; as it is not universal it can 

 hardly be a' necessary relationship. In Paramcecium, as we have just 

 seen, nuclear reorganisation can bring about a fresh cycle of fission 

 equally as well as conjugation. In the higher phyla of the animal 

 kingdom the close association of fertilisation with reproduction has 

 completely obscured their primitive relationships and significance. 



■ . The supposed Chemotactic Properties of Spermatozoa and 

 THEIR Relation to the Phenomena of Fertilisation 



It has been suggested that the spermatozoon is attracted towards 

 the ovum by a chemotactic action which the metabolic products of 

 the latter are able to exert upon the former. Pfeffer's experiments * 

 upon the spermatozoa of ferns are usually cited as evidence of this 

 view. 



Pfeffer observed that malic acid, when put into a capillary tube 

 with one end open and placed in a drop of liquid containing fern 

 spermatozoa, has a strong attractive influence upon these organisms, 

 causing them to swim in large numbers into the opening of the tube. 

 He concluded, therefore, that it is the malic acid in the archegonium 

 of the fern's ovum which causes the approach of the spermatozoa. 



According to Strasburger,^ the ova of the Fucaceae also possess 

 chemotactic properties, attracting the spermatozoa from a distance 



> Allison, The British Thoroughbred Morse, London, 1901. 



2 Wallace (R.), Argentine Shows and Livestock, Edinburgh, 1904. Of. also 

 Darwin, Animals and Plants, London, 1905. 



' Huth, The Marriage of Near Kin, 2ndJEdition, London, 1887. 



* Pfeffer, " Locomotorische Richtungsbewegungen durch chemische Reize," 

 Untersuchungen aus. d. Bot. Inst, zur Tubingen, yol. i., 1884. 



° Strasburger, Das botan. Prakticwm, Berlin, 1887. 



