SOME OBSERVATIONS AND CONSIDERATIONS 



UPON THE MATURATION PHENOMENA 



OF THE GERM CELLS. 1 



THOS. H. MONTGOMERY, JR. 



In a series of studies on the spermatogenesis of the Hemiptera, 

 of Peripatus 3 and of the Amphibia, 4 I have endeavored to prove 

 the following points : 



1. That the chromosomes retain their individuality from gen- 

 eration to generation to that extent that a chromosome of one 

 generation is not a new formation, however much its chemical 

 substance has became changed by metabolism, but represents at 

 least a part of a particular chromosome of the preceding genera- 

 tion. 



2. That the first maturation mitosis in the species studied re- 

 sults in the separation from each other of entire univalent chromo- 

 somes, and hence is a transverse or reduction division ; while the 

 second maturation mitosis results in the longitudinal splitting of 

 univalent chromosomes, and therefore is an equational division. 



3. That the so-called "reduction in number" of the chromo- 

 somes is effected before the maturation divisions, by a pairing 

 (conjugation) in the early growth period (synapsis stage) of the 

 spermatocytes, of univalent chromosomes of like volume, each 

 such composite chromosome then being bivalent with relation to 

 the number in the spermatogonia. 



4. That this conjugation of univalent chromosomes in the 

 synapsis stage, is a conjugation of paternal with maternal chromo- 



1 Contributions from the Zoological Laboratory of the University of Texas, No. 54. 



2 " The Spermatogenesis in Pentatoma up to the Formation of the Spermatic!," 

 Zoolo<r. Jahrit., 12, 1898 ; " Chromatin Reduction in the Hemiptera : a Correction," 

 Zoolog. Aitz., 22. 1899 ; "A Study of the Chromosomes of the Germ Cells of Meta- 

 zoa," Trans. Amer. Phil. Soc., 20, 1901; "Further Studies on the Chromosomes 

 of the Hemiptera heteroptera," Proc. Acad. Nat. Sci., Philadelphia, 1901. 



3 "The Spermatogenesis of Peripatus (Peripatopsis) balfouri up to the Formation 

 of the Spermatid," Zoolo^. Jahrb., 14, 1900. 



4 " The Heterotypic Maturation Mitosis in Amphibia and its General Significance," 

 BIOL. BULL., 4, 1903. 



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