114 



FUNDAMENTALS OF CYTOLOOY 



.spindles. In many cases they are longer than they were in metaphase /, 

 and this, together with their simpler structure, causes division // to 

 resemble a somatic mitosis much more closely than division I does. In 



Fig. 84. — Stages in meiosis in angiospeiuii microsporocytes. 1, transverse section of 

 lily anther with sporocytes. 2, metaphase I in May apple. 3-5, anaphase /, metaphase 

 II, and anaphase II in lily. Cliromosome doubleness is obscured by fixation in 4. 



the anaphase the chromatids of each dyad move apart to the spindle poles, 

 thus completing the meiotic distribution of the chromosomes. 



Telophase II. — The four groups of chromosomes now reorganize as a 

 quartet of nuclei. Each of them contains one complete genome, this 



Fig. 85. — Meiosis and syngamy in a threadworm {Ascaris). 1, metapliase of first 

 meiotic division in oocyte; two tetrads present. The sperm has already entered the egg (at 

 left); the smaller dark body is its nucleus. 2, 3, second meiotic division; first polar body 

 disintegrated above; sperm chromosomes near center of egg. 4, sperm and egg nuclei 

 about to unite; first polar body above and second one below because of rotation of egg. 

 During these stages a perivitelline space develops between the thickened wall and the egg. 



genome being composed of one chromatid (now a chromosome) from each 

 of the tetrads present in metaphase I. Each chromosome has the 

 chromonemal doubleness which will become effective in the ensuing 



