Vol. XL VI April, IQ24 No. 4 



BIOLOGICAL BULLETIN 



THI-: m.HAVInR OF THE NUCLEUS AND CHROMO- 



SOMI.s DURING SPERMATOGEXESIS IX THE 



ROBBER FLY LASIOPOGOX BIVITTATUS. 1 



< HAS, \V. METZ AND JOSE F. NONIDEZ. 

 CARM'.ii [NST11 WASHINGTON, DEPARTMENT OP GENETICS, AND CORN 



avERsiTY MEDICAL COLLEGE. 



INTRODUCTION. 



tin- growth period of the primary sperm. itocytes in 

 Ln\ii'(>"['ini hii'nttulns L\v., 2 nuclear changes occur which trans- 

 form tlu- -pherical nucleus into a series of ramifying ch.nnl 

 endo-in^ i he chromosome threads. Conditions in these nucK-i 

 gesl th.ii tin- -taiiuible threads are axes or cores of cr >n-iderably 

 IT liodit -, which are mainly hyaline. The pre-ent account U 

 com niicd primarily with these features, although it include- a 

 ill -' ripti'iii >t' >|)ermatogenesis up to the second s|>-nn.it<.cyu- 

 di\ i-imi. 



The nl.-ervations are based on two specimen-, collected ne.ir 

 Slit i id. in. Wyoming. Both were fixed in strong l-'leinmin^ and 

 >t. lined v> ith iron ha?matoxylin. One (_'"-- was counterstained 

 \\ith lij;ht screen. The technique employed w.is the -.nne .1- that 

 refill. irly used in preparing dipteran material, and the fixation is 

 i^ood in luith specimens. So far as we know the peculiar nuclear 

 behavior is characteristic of the species and does not represent 

 an accidental abnormality. 3 



\ pn-liminary account of tli; .<-n U-lnn.- t ; ;iu nt.il 



Biology and Medicine and published in tlir Socift;.'- I'r. ici-i-dini; and 



Nonidcz, '22). 



* \Y. li-liti-d to Mr. Jus. R. Hine for thr specie-; 'l.-tcrniinatioti. 



' This is supported by the fact that conditions sonii-uliat similar have been found 

 in tun t'thri < 'f Mies (.discussed below). In these our material : ntly 



extensive to prove that the conditions are normal. 



153 



