631 



into only half the normal number of chromosomes. I showed for Peri- 

 patus (1900), on the contrary, that a continuous linin spirem is present 

 at this stage but not a continuous chromatin spirem, and that the 

 bivalent chromosomes are produced by a later conjugation without 

 the formation of a continuous chromatin loop. According to Riickert 

 it is a case of chromosomes already closely connected remaining so; 

 according to me, of chromosomes not in contact at first becoming so 

 secondarily. Hence I spoke of this act as the "conjugation" of the 

 chromosomes, and argued that this is the important criterion of the 

 synapsis stage. 



Then Prof. Haecker writes (p. 190): «Dagegen wird die von 

 Montgomery vertretene Anschauung, daß die schließliche Paarung 

 der Chromosomen die Verjüngung (rejuvenation) derselben zum 

 Zwecke habe (1901. S. 223), sich heut zu Tage kaum mehr ungetheilter 

 Zustimmung erfreuen, nachdem die Grundlagen der Verjüngungs- 

 theorie von verschiedenen Seiten mit so triftigen Gründen angefochten 

 worden sind.« I argued in line with the conclusions of Maupas (1889) 

 and R. Hertwig (1889) that a very essential result of the act of ferti- 

 lization is rejuvenation of the gametes, occasioned by the new inter- 

 mixture of living substances; and that the conjugation of the chromo- 

 somes in the synapsis stage of the spermatocytes is the last part of the 

 fertilization process. An objection can be brought to this view from 

 the work of Calkins (1902) on Paramoecium. Calkins shows that 

 without conjugation of two individuals a new cycle of reproduction 

 may be initiated by the stimulus of foods, and argues accordingly 

 that periods of reproductive activity may be inaugurated by other 

 factors than conjugation. No one will dispute this point. But it by 

 no means disproves that fertilization, conjugation of individuals, arose 

 and was perpetuated because by the the interchange of substances 

 each conjoint became thereby refreshed. Similarly with the cases of 

 artifically fertilized eggs, where the eggs are stimulated to cleavage 

 by various chemical solutions, experiments made first by R. Hertwig; 

 such experiments do not at all prove that the spermatozoon is unessen- 

 tial in fertilization , nor yet that the essential part process in fertiliza- 

 tion is simply an induced change in the chemical nature of the egg. 

 The fact remains that all Metazoa, and all the Protozoa for which the 

 life-history is known, have, at least periodically, a process of fertili- 

 zation by the conjugation of two individuals (the mature germ cells 

 being necessarily individuals). It is from such experiments on induc- 

 ing eggs to cleave by means of unnatural agencies , that there has 

 grown up, but very unreasonably, a doubt as to the value of the factor 

 of rejuvenation in fertilization. I pointed out that immediately after 



