No. 463-] STUDIES ON PLANT CELL. VI. 491 



duce the terms "maiosis" and the "maiotic phase" to cover the 

 whole series of nuclear changes included in the heterotypic and 

 homotypic mitoses. The maiotic phase is regarded _as_ similar 

 in its essential details in both animals and plants but the fact of 

 its appearance at different points in the life histories precludes 

 any probability of relationship in such widely divergent lines. 

 The events of synapsis and the consequent peculiarities of the 

 heterotypic and homotypic mitoses are considered as intercalated 

 between the series of typical mitoses in the life history. 



Farmer and Moore's conclusions for Lilium c (indicium may be 

 briefly summarized as follows. A definite spirem with the 

 chromatin distributed as granules appears in the young spore 

 mother-cell before its separation from neighboring elements. A 

 " first contraction figure " now appears and the spirem thread 

 becomes densely coiled in the vicinity of the nucleolus, this con- 

 dition persisting for some time. Then the coils of the spirem 

 loosen and become distributed about the periphery of the nuclear 

 cavity, from the point of contraction as a center. A longitudi- 

 nal fission of the spirem thread then appears, the chromatin 

 granules dividing so that they come to lie in two parallel rows 

 on the edge of the split ribbon. The fission is irregular and 

 open loops appear at places. The spirem then shortens and the 

 split gradually closes up and becomes very difficult to recognize. 

 Many of the convolutions of the thread are attached to the 

 nuclear membrane while the remainder form a tangle in the 

 interior around the nucleolus which is believed to give up much 

 of its substance to the chromatic portion of the spirem. Farmer 

 and Moore then fail to find the double thread and its union dur- 

 ing synapsis to form a single (fusion) spirem which is a funda- 

 mental feature of Allen's account. 



There follows then a stage which has been the subject of 

 much discussion. According to Farmer and Moore the spirem 

 thread becomes pulled out into V- and U-shaped loops, shown 

 with especial clearness where the bend of the loop is attached to 

 the periphery of the nuclear membrane. The arms of the V's 

 then come to lie parallel and so close together as to give the 

 appearance of a fission in a structure which is really the result 

 of an approximation of the two free ends of what was a loop. 



