FERTILIZATION IN PLANTS AND UNICELLULAR ORGANISMS 337 



Meantime all we can gain from it is a certain mistrust of the 

 interpretation of the processes of maturation in Artemia which have 

 hitherto been given; at least we are tempted to suppose that the 

 copulation of two nuclei which Brauer observed in Artemia may not 

 have led to the formation of the segmentation nucleus there either, 

 but may have had some other significance. 



But, even if we leave this point entirely out of account, there 

 remain all the cases of regular parthenogenesis in which this mode of 

 reproduction occurs alone and not in alternation with the sexual mode. 

 In these only one maturing division is undergone, and only one polar 

 body is formed, and thus 

 there can be no possibility 

 of supposing a self-fertili- 

 zation of the ovum. 



It is possible that we 

 may yet discover species 

 among unicellular organ- 

 isms which multiply with- 

 out limit ia the absence of 

 any amphimixis. E. Hert- 

 wig has recently observed 

 phenomena in Infusorians 

 which he is inclined to refer 

 to the suppression of an 

 earlier habit of conjugation, 

 and so to a kind of partheno- 

 genesis. But even if it 

 should be shown that am- 

 phimixis plays a part regu- 

 larly and without exception in the life of all unicellular organisms, 

 the facts in regard to multicellular organisms are not affected ; and, 

 finally, the process of amphimixis is one which we have not the 

 slightest ground for assuming to be either an awakener or a maintainer 

 of life, and so I return to the most essential part of the whole problem, 

 the meaning of the chromatin structures, the combination of which 

 is the undoubted result of amphimixis. Do they really represent, 

 as we assumed earlier, the hereditary substance, and what do we 

 mean by this term ? 



As far as I know the literature and the development of biological 

 theories, the botanist Nageli was the first to deduce, from the consider- 

 able difference in size between the egg-cell and the sperm-cell, the 

 conclusion that the material basis on which the hereditary tendencies 



Fig. 79. The two maturation diviiions in tlie 

 unfertilized (drone-forming) egg of the bee, after 

 Petrunkewitsch. Rsp 1, first polar-body in division. 

 K I and K 2. the two daughter-nuclei thereof. 

 i?sp 2, second directive spindle. K 3 and K 4, the 

 two daughter-nuclei tliereof. In the subsequent 

 stage K 2 and K 3 unite to form the primordial 

 sex- cell nucleus. Highly magnified. 



