VilalUij and Orgdnizalion of Protoplasm. 79 



the bisexually re^titlltive process, started and governed by the two cen- 

 trosomes of the sperm-plasm. At each stage of its evolution the sperm- 

 plasm assimilates congruous egg-plasm, the process ending in the for- 

 mation of the two bisexual and unilaterally potential blastomeres. 



The interpretation of fertilization here oll'ered flows likewise con- 

 sistently from the nature of the living substance, as positively demon- 

 strated in the first section. It has to be added, that, as in normal and 

 artificial parthenogenesis, the two first blastomeres form around germi- 

 nal centrosomes arising within egg-plasms, it seems that even in some 

 cases of fertilization the egg-plasm takes the lead in the bisexually 

 blending and reproductive process. This appears to have been the case 

 in Wheeler's observation of what takes place during fertilization of 

 Myzostoma. And it may possibly happen more frequently than at 

 present supposed. If this were found to be the case, it might suggest a 

 scientific explanation of sex-determination. Indeed there is no theo- 

 retical objection to egg-plasm-activity taking at times the lead in the 

 process of fertilization and ontogenetic evolution, as it is otherwise so 

 readily induced to do so in parthenogenetic self-evolution. Though this 

 suggestion is supported by various experiences, of course only direct ob- 

 servation can have weight in the decision of such a question. 



In every case of ontogenetic segmentation the nucleus itself remains 

 passive, and is drawn into the formative activity by non-nuclear plasm. 

 The chromosomes, the only enduring constituents of the nuclear plasm^ 

 are, however, bearers of an indispensable function, though not of for- 

 mative import. As already suggested, it is likely connected with the 

 vital j)rocess of_oxydation, which suggestion is supported by the blood- 

 corpuscles being of nuclear origin. 



THE PROBLEM OF THE LIVING FORM. 



The blending of two or more Protozoa into a proportionately enlarged 

 individual without disturbance of the specific structure of the species, 

 is a fact of nature readily observable. This occurrence proves that the 

 specific form of protoplasmic beings is not directly dependent on the 

 amount of substance entering into it. Driesch succeeded in bringing 

 about the union of two segmented eggs of Echinus, and obtained perfect 

 single individuals. Zur Strassen obtained giant embryos of Ascaris 

 formed by the fusion of two eggs. The remarkable results of exjieri- 

 ments attained by grafting point to the fact, that the more or less inti- 

 mate blending or coalescence of the living substance of difl;erent indi- 

 viduals is dependent on specific complemental affinity attaching to the 

 chemical constitution of the substance of the coalescing organisms or 

 fragments of the same. 



The highly significant fact, that organic form and structure is not 

 directly dependent on the amount of formative material entering into 

 their constitution, is most strikingly revealed in the production of com- 

 plete embrA-onic forms from almost any fragment of egg-plasm, which 



