REPTILIAN SPERMATOGENESIS 301 



(If the conclusions drawn from a study of spermatogenesis are 

 correct, then the female of this species should have fourteen 

 macro-chromosomes, that is, two extra chromosomes, which are 

 equal to an additional X-chromosome. See p. 307 for further 

 discussion of this point.) 



Before examining the somatic divisions of embryos, the chro 

 mosome complex of the male germ cells should be carefully 

 examined. In the adjacent text figure 5, A and B (also plate 

 3), we have drawings of two spermatogonial divisions. It will 

 be noted that there are ten large conspicuous chromosomes 

 which have a V shape, two small V's labeled 'b,' and ten small 

 elements, the micro-chromosomes. It is not always easy to dis- 

 tinguish the small 'b' chromosomes from the largest micro- 

 chromosomes, because occasionally, and this is especially true 

 of somatic divisions, the larger micro-chromosomes also have 

 a V shape. The ten large macro-chromosomes, however, are 

 conspicuous and easily identified, and since the X-element comes 

 from a pair of these, we may disregard the 'b' chromosomes and 

 the micro-chromosomes in the following description. If the 

 X-element has been correctly identified in the spermatogenesis, 

 then the female should show twelve large V-chromosomes and 

 the males ten. 



The four embryos, from which the cells shown in text figure 

 5, C to H, were taken, were all obtained from one female, pre- 

 served in the same dish of cold Flemming, carried through dehy- 

 dration in the same vial, embedded in the same paraffin block 

 side by side, and stained on the same slide. In studying embryos, 

 one individual at a time was followed, camera drawings made 

 of the chromosome elements, and afterwards these were compared 

 and checked up. The number of large V-shaped chromosomes 

 was constant for a given embryo. Occasionally one of the V- 

 elements was apparently broken in two, but as the two halves 

 were adjacent, it caused no confusion (text fig. 5, H). I did 

 find, however, some variation in the shape, size, and number 

 of the micro-chromosofnes in the same individual. In one cell, 

 for example, the normal number (ten) of micro-chromosomes 

 would be seen, while in an adjoining section a cell would be 



