316 



GARY N. CALKINS 



of maturation have only two nuclei which complete the division 

 process in each individual. 



After the telophase of the first maturation division, the nuclei 

 do not reform the dense homogeneous nuclei characteristic of 

 the early stages of conjugation. They become mope compact, but 

 remain vesicular with a strong staining capacity. The chroma- 



Figs. 45 and 46 Two pairs with different types of Mrst maturation nuclei. 

 X 800. 



tin at first is in a rather dense reticulum (figs. 54, a). It then 

 collects into eight chromatin aggregates with irregular shapes, 

 distributed throughout the nucleus. These aggregates are trans- 

 formed into elongate rods or chromosomes (figs. 54, b, c, d) . 



The full history of this second maturation spindle is extremely 

 difficult to w^ork out. During its division, the number of chrom- 

 osomes is reduced from eight to four, as proved by the four 



