THE BEGINNING OE PROPHASE 89 



centromeres orientated with regard to one another in the arc axes 

 of the spindle. 



(h) (First) Anaphase. The centromeres of each pair pass to 

 opposite poles, each drawing after it the pair of attached chromatids 

 so that in segments distal to a chiasma paired chromatids are 

 separated. At the same time the attractions between paired 

 chromatids usually lapse even where they are not forcibly drawn 

 apart. 



(i) [First) Telophase. The chromosomes form two daughter- 

 nuclei at the poles, uncoiling and passing into a resting stage, the 

 interphase, two separate cells being formed. The two daughter- 

 nuclei each have the haploid number of chromosomes, but, since 

 these are already divided, they have the diploid number of chro- 

 matids as in a mitotic telophase. 



11. Second Division. (;) (Second) Metaphase. At an early 

 stage the two chromatids are widely separated — more so than in 

 any somatic mitosis. They are then held together only at their 

 centromeres. Later stages resemble mitosis, but metaphase is 

 rapid and the chords never associate completely. 



(k) (Second) Anaphase. The chromosomes are distributed as at 

 an ordinary mitosis. 



(/) (Second) Telophase. Four daughter-nuclei are formed, each 

 receiving the haploid number of chromatids. 



3. MEIOSIS IN DIPLOIDS 



(i1 The Pairing of Chromosomes. The prophase of meiosis 

 begins after a resting stage which may be short or almost entirely 

 omitted, so that the chromosomes which appear can be traced 

 directly to telophase chromosomes whose individuality has never 

 been even entirely lost. In the spermatogenesis of certain Orthop- 

 tera and Hemiptera, for example, the nucleus continues divided into 

 as many compartments as there are somatic chromosomes until the 

 prophase chromosomes appear (Wenrich, 1916, Phrynotettix ; Renter, 

 1930, Alydus ; Chickering, 1927, Belostoma, etc. Cf. Ch. II). One 

 chromosome comes from each compartment. It consists of a series of 

 darkly staining granules, the chromomeres, of unequal sizes lying at 

 unequal distances in a lightly staining thread (Plates V, XV, Fig. 29), 



