OOGENESIS IN THE WHITE MOUSE 297 



this view have used the behavior of the chromosomes to explain 

 certain modes of inheritance and have constructed compHcated 

 theories to account for the facts. It would seem, however, that 

 they have confused the explanation of the phenomena with the 

 teleological significance they have attached thereto. 



Another school (Meves, Duesberg, et al.) avoids the difficulty 

 of explanation or interpretation by denying the facts. For them, 

 synizesis is merely a tendency on the part of the chromatin to 

 contract, at a certain period in the development of the germ 

 cells, and the contraction figure is due to imperfect fixation in a 

 faulty technique. Synapsis does not exist; those who describe 

 this condition have confused the sedation of stages, and the 

 apparent conjugation is really a splitting and separation of chro- 

 matin threads, a precocious preparation for the following divi- 

 sion (first maturation division). 



A third view is that attributed to R. Hertwig by von Wini- 

 warter and Sainmont ('08), by Kingsbury and Hirsch ('12) and 

 by Levy ('15), although I have been unable to find the reference 

 where he discusses just this point. This view is that synizesis 

 and synapsis represent a suppressed or abortive mitosis. 



According to this view, on the one hand, synizesis represents 'an 

 attempt on the part of the spermatogonia to divide again — which 

 fails; while on the other hand, the reputed conjugation of chromosomes 

 occurring at about this time is but the imperfect fission and subsequent 

 fusion of daughter chromosomes of such abortive division (Kingsbury 

 and Hirsch, '12). 



In discussing the degeneration of secondary spermatogonia in 

 Desmognathus, Kingsbury and Hirsch point out a resemblance 

 between the degeneration stages and synizesis, and make the 

 suggestion that synizesis may represent or be an expression of a 

 "running out of the spermatogonial stock." It may be the check- 

 ing or terminating of the period of multiplication. Synapsis is 

 apparently absent in Desmognathus. 



If synizesis and synapsis represent an abortive mitosis, it 

 would be expected that somatic cells would show similar phenom- 

 ena under the proper conditions. And, indeed, the conclusions 

 of Marcus ('07) as reported by Popoff ('08) demonstrate this. 



