282 THEOPHILUS S. PAINTER 



to be the reduced chromosome number of the female. These 

 two examples are typical of the confusion found at present in 

 this field. 



The difficulties which have confronted workers in vertebrate 

 spermatogenesis are well known. The vertebrate germ cells 

 have been, in the past, the most difficult of all tissues to fix 

 properly for chromosome studies. The number of chromosomes 

 in every case so far reported on is relatively large, and there 

 is a very pronounced tendency for the chromosomes to fuse 

 together in the spindles so that accurate counting usually 

 has been impossible. Recently, however, through the inves- 

 tigations of Allen ('16, '19) and Hance ('17), some real advances 

 in technique have been made, so that, with care, much of the 

 difficulty experienced by earlier writers may be overcome. With 

 the reinvestigation of the common vertebrates with these new 

 methods, we may confidently expect that the present confusion 

 will be cleared up to a large extent. 



The reptiles are the only large class of vertebrates that have 

 not been extensively studied by cytologists with a view of deter- 

 mining the condition of the sex-chromosomes. With the excep- 

 tion of a brief note by Jordan ('14) describing the results of his 

 work on the spermatogenesis of the turtles, Chrysemys marginata 

 and Cistudo Carolina,- the reptiles present a virgin field for the 

 investigator. 



The following paper presents the results of an extensive study 

 of the spermatogenesis of a number of lizards made during the 

 past two breeding seasons, and, in addition, a study of dividing 

 embryonic cells, made in order to check up certain conclusions 

 regarding the sex-chromosomes.^ In making this study the author 

 had two main objects in view: First, as we knew nothing about 

 the sex-chromosomes of lizards, it seemed desirable to fill out 

 this chapter of our knowledge. The second consideration was 



2 A complete account of this work has never been published. Professor 

 Jordan, however, very kindly sent me his manuscript together with the figures, 

 and from time to time I shall refer to the conditions found by him in the turtle. 

 ' ' The main facts concerning the spermatogenesis of Anolis carolinensis were 

 presented before the American Society of Zoologists, December 28, 1919. See 

 Anat. Rec, vol. 17, for abstract of paper. 



