REPTILIAN SPERMATOGENESIS 313 



Whatever the explanation be for the micro-chromosomes, it 

 is clear that the macro-chromosomes of all the Iguanidae are 

 all strikingly alike, and they give additional evidence for the 

 validity of McClmig's generalization which was based on a 

 study of grasshopper chromosomes. 



If. Syncytial masses 



A very striking feature of the testes of all lizards is the common 

 occurrence of so-called syncytial masses. Similar bodies have 

 been reported for turtles (Jordan), birds, and mammals. 



In lizards these masses are most clearly seen in well-matured 

 individuals where the lumen of the tubule is large. In such 

 cases germ-cells tend to scatter somewhat from the walls of the 

 tubules, and one finds here and .there rounded masses of cyto- 

 plasm containing from two to eight or more nuclei, but with no 

 distinguishable cell walls. Typically, one finds two primary sper- 

 matocytes thus associated (text fig. 6, A). Occasionally there 

 may be more primary spermatocyte cells. Figure B shows such 

 a syncytial mass, as seen in A, undergoing division. Masses 

 showing secondary spermatocyte cells have from six to eight 

 nuclei, and many spermatids may be joined in this fashion. 



The formation of these syncytial masses is probably due to 

 the failure of the cytoplasm to divide after the chromosomes have 

 separated. However, it does not seem to interfere with the 

 normal formation of spermatozoa, for one finds such masses as 

 shown in figure C where the formation of the sperm heads is 

 going on normally. ^^ 



In passing, attention should be called to interesting theoretical 

 possibilities which such a figure as 6, B, affords. Here are two 

 first spermatocyte spindles lying closely associated side by side. 

 It must be a very rigid division mechanism which would prevent 

 at some time a chromosome from getting into the wrong spindle. 

 This would seem to give a mechanism for variation in chromosome 

 number, and if the sperm thus formed were viable would give 



^" In this connection it is interesting to note that Jordan has found the same 

 condition in the turtles. He describes two, three, or even four sperm arising 

 from the same cytoplasmic mass^. 



