208 BOTANY 



spireme became considerably thickened whilst it was still con- 

 tracted into a knot. The synizetic knot then loosened out, and 

 this was accompanied by thickening of the spireme. The open 

 spireme stage was passed through with rapidity, and the second 

 contraction was ushered in. The spireme shortened and thickened 

 and became drawn into a dense knot which lay near the nucleolus. 



When the folds of this knot gradually unloosened, it was seen 

 that not only had the thread become divided into a number of 

 thickened areas, each a chromosome, but that several pairs of 

 chromosomes had become cutoff from the main part of the spireme, 

 although they might still be interlocked with it (Fig. 76, 2). 

 The spireme was still in contact with the endonucleolus, and the 

 nucleolus at this stage had completely lost its affinity for stains. 

 At diakinesis the nucleolus still persisted as a pale non-staining 

 biconvex body, lying opposed to the nuclear membrane. The 

 spireme now broke away from the nucleolus and at the same time 

 the endonucleolus disappeared. When the second contraction 

 knot had completely loosened out, it was seen that the spireme 

 had become constricted into fourteen chromosomes. Eight of 

 these segmented off in pairs from the main part of the spireme. 

 The chromosomes of each pair bent round so that they were 

 approximately parallel to each other and those which were 

 presumably free ends had usually become attached, so that each 

 bivalent took the form of a small ring. The remaining six chromo- 

 somes, which were still joined together end-to-end, also formed 

 themselves into a ring. It was ascertained that the ringed pairs 

 might be interlocked with each other or with the main spireme, 

 or they might be entirely free. The chromosomes were of a 

 spongy nature, those forming the large ring being connected by 

 fine threads. During diakinesis the chromosomes condensed and 

 lost their spongy texture. 



The behaviour of the nucleus at this stage, and in all the subse- 

 quent stages of the reduction division, was identical with that 

 of the nuclei in the mother-cells on the male side. Occasional 

 irregularities were found to occur during meiosis, such as non- 

 disjunction, double non-disjunction, lagging and fragmentation 

 of the chromosomes. No resting nuclei were found during 



