author's abstract of this paper-issued 

 by the bibliographic service, october 17 



STUDIES IN REPTILIAN SPERMATOGENESIS 



I. THE SPERMATOGENESIS OF LIZARDS^ 

 THEOPHILUS S. PAINTER 



SIX TEXT FIGURES AND FOUR PLATES (FORTY-EIGHT FIGURES) 



INTRODUCTION 



Cytologists are well agreed that our knowledge of the chromo- 

 somes, especially of the sex-chromosomes, of vertebrate animals 

 is in a very conflicting and unsatisfactory state. A critical 

 review of the literature will show that, while the spermatogenesis 

 of most of the common vertebrates has been worked upon, with 

 a view of determining if sex-chromosomes were present, much 

 of the work has been fragmentary in character, and various 

 criteria have been used for identifying the sex-chromosomes 

 (such as nucleoli in spireme stages, dimorphism of sperm, or the 

 early movement of one chromosome to one pole in a maturation 

 division). Too frequently conclusions have been based upon a 

 few dividing first spermatocyte cells, without checking up such 

 observations on cells of the following division or without a study 

 of the female chromosome complex. In only a few vertebrates 

 is the somatic or diploid number of chromosomes definitely 

 known. Even in forms where the spermatogenesis has been 

 most carefully and completely worked out, as in the pig or the 

 opossum, there is a wide divergence of opinion as to the conditions 

 existing. Thus Wodsedalek ('13) gives 18 as the diploid number 

 of chromosomes for the male pig, while Hance ('17), using an 

 improved technique, shows that there are 40 chromosomes both 

 in the germinal and the somatic cells of this animal. Jordan 

 ('12) gives 9 as therhaploid number of chromosomes for the male 

 opossum, while Hartman ('19), working upon ova, found 12 



^ Contribution no. 149 from the Department of Zoology, University of Texas, 

 Austin, Texas. 



281 



