The Spermatogenesis of Hybrid Peas 521 



FlIXBASKET AND DeBARBIEUX, PuRE RaCES 



No difference in the ori^^in and development of the microspore 

 was noted between the pure races Fillbasket and Debarbieux. In 

 both the reduced number of chromosomes was seen to be the 

 same, namely seven, and the chromosomes appeared to be quite 

 aHke in each ; to avoid repetition the general account of the matu- 

 ration processes will be deferred until the next topic. Favorable 

 material, however, gave opportunity to observe the sporogenous 

 divisions in Fillbasket and the results are here presented. 



In the most of the sporogenous divisions the mitotic figures 

 are likely the same as in the somatic nuclei ; but in late anaphases 

 or early telophases certain characters were seen which were appar- 

 ently somewhat different. In early telophase of one of the later spor- 

 ogenous divisions the chromosomes are associated in pairs, touch- 

 ing by one, the polar, end. A nucleus with such chromosomes is 

 shown in /. 4. This division was evidently the last sporogenous 

 one, that is, the nucleus figured would become that of the spore 

 mother-cell without further division. Whether the chromosomes 

 are ever in touch throughout their whole length, as appears to oc- 

 bur in Fillbasket x Debarbieux (/. 6), was not determined. The 

 later history of the chromosomes is of great interest, since upon a 

 proper understanding of it may depend an appreciation of the sig- 

 nificance of the loops of chromatin which appear subsequently in 

 the nucleus as one of the prophases of the first maturation di- 

 vision. If, as supposed, the spireme of the nucleus of the spore 

 mother-cell is double, we might look for a previous doubling of 

 the chromosomes, although this might perhaps not follow. I have 

 seen no clear indication that the chromosomes form a double 

 spireme in the telophases of the last sporogenous division. The 

 behavior of the chromosomes at this time is as follows : As they 

 approach the poles of the spindle they are appreciably more uni- 

 formly arranged and more nearly parallel to the long diameter of 

 the spindle than in the other divisions in the sporogenous cells, 

 when at the poles the chromosomes unite or touch two and two 

 by the polar ends. In this condition they enter the resting stage ; 

 a continuous spireme was not seen. In some nuclei the adjoining 

 pairs of chromosomes were apparently united by their free ends, 

 but I did not surely determine this point. If the chromosome 



