The Beginning and End of Life 40 1 



Porms which reproduce normally. This he unhesitatingly 

 affirms, and stakes the validity of his view upon the alleged 

 fact that while two ' polar-bodies ' are expelled from ordinary 

 fcva, all parthenogenetic ova expel but one. 

 " The ova of animals of the most varied kinds (but not so 

 far as known of all classes) agree in the performance of a 

 process, the meaning of which is much disputed. As each 

 ovum becomes ripe for fertilisation it extrudes from one end, 

 or ' pole,' a minute particle of its substance, and, a little later, 

 another apparently similar. These extrusions Professor Weis- 

 mann explains as nevertheless being of quite different natures. 

 He declares that every ^^'g contains two substances — one 

 devoted to the completing the structure of the ^'gg itself, and 

 the other substance to the formation of the future young. 

 The first particle excluded he declares to be formed of the egg- 

 making substance only ; while the second he considers to be 

 part of the essential reproductive substance, or germ-plasm 

 of the ^gg. When this is, as usual, extruded, then, according 

 to him, there does not remain enough of the germ-plasm for 

 the formation of the embryo. This sufficiency must be made 

 good by the addition of similar germ-plasm from without, 

 and such he deems to be the only meaning of fertilisation. 

 When, however, the second particle is not excluded, then, he 

 says, enough substance exists for development without an}^ 

 addition from another source, and hence parthenogenesis 

 takes place without difficulty. Now, in the first place we 

 must observe his assertion that there are two such different 

 substances in the ^dgg is a mere hypothesis without a shadoA\r 

 of proof; and in the second place his assertion that the two 

 particles extruded are really different in nature though ap- 

 parently alike, is another mere hypothesis without a shadow 

 of proof. But there is not merely an absence of proof, there 

 is now proof to the contrary. Amongst the creatures which 

 are parthenogenetically produced is the male, or drone, of 

 VOL. II. 2 c 



