PRESENT PROBLEMS I\ EVOLUTION AND HEREDITY. 371 



brothers ii]>oii iicrm cell ]>liysi()l()oy and 'patlioloiiy, wiiicli are full of 

 sugg'estiou as to the (causation ol" abnorinalities in inlieiitance. These 

 were Iteyiin in 1884, and were first directed to the intlncnce of gravita- 

 tion npon the plam^s of embryonic cell division, foHowinii- up the ex- 

 periments of Plliiiier and Ifauber. In 1885 the conditions of bastard 

 fertili/at ion were studied; in 1887 the causes of i)olyspermy or mul 

 tiple fertilization; and in 18110 the effects of extreme lieat and cold 

 u])on j>erm-cell functions.* In general the conclusions reached were 

 that in the normal state there exist regulating forces in the ovum which 

 prevent multiple fertilization or bastard fertilizations (/. c. by sperma- 

 tozoa of other varieties), but these forces are neutralized where the 

 life energy of the cell is diminished by reagents or by extremes of 

 temj)erature. 



For example, in the normal state the entrance of a single s})erma- 

 tozoon produces a reaction in the ovum wall ])reventing the eiitiance 

 of other spermatozoa, but when the ovum is Meakened by chloroform 

 solution two or more spermatozoa enter before the reaction aj)pears; in 

 fact that degn'c of polyspermy is directly proportional to the intensity 

 of the chemical, thermic, or inechaui(;al disturliance of the ovum. 

 Double fertilization or over-fertilization has not in a single case resulted 

 in tlie productiiui of twins, so that l^'oFs sup])ositioii is negatived, 

 although other forms may behave differently. The cell function may 

 be arrested at any stage by thermic intiuenccs; thus two pronuclei, 

 l)aternal and maternal, alxmt to unite, can l)c held apart by lowering 

 the tem])erature, i*olyspermy also results from a lowered tempera- 

 ture. It is noteworthy that the conditions of bastard fertilization and 

 polyspermy arc different; chloroform produces the latter but not the 

 former. Ku])ffer has, I believe, smx-eeded in producing twins, or 

 rather two headed monsters, by abnormal fertilization in tishes. 



These researches, although made with a different ol»jcct. i('-estal)lish 

 the older views as to the inter-de))cndcnc<'of nucleai- and extra-nu(;lear 

 activities, and show that no sharj) line oi demarcation of function can 

 be drawn between the nnclcnsasa center !>f rcpr(>dnction and heredity 

 and the cytoplasm, as the seat of tissue building and nutrition. In 

 Boveri's disco\'er>- of tin' archo-])lasmic centers, or centrosomcs. we find 

 positi\«' ground lor this broadci' xicw. It is connt'clfd with the cell 

 l)hcnomena of heredity in the following manner: 



While the union of the nuclei in fertilization is the most obvious 

 featun'. this union is dependent upon the archoplasm, which re-arranges 

 the nuclear elements. If the spermatozoon contains no archo])lasm, 

 this power can not come from the ])arental side; but Uoveri shows that 

 this is probably not the case and that the si>ernuitozoon brings its cen- 

 trosoine with it. thus entering the ovum with both the parental chro- 

 matin substance and dynamic material. It is certain from this and 



*Experiinent('lic l'iitcrsiii'lmiit;'»n iilicr die Bedinyiiiiyen dcr IJaslaidbfl'nuhtmig. 

 .Ic'.ia, 1885. See scries of jiapers in JtnoUche Zvitfickv'iJ't. 



