216 KIYOSHI MASUI. 



of the horse aud of cal^tle. From iiu accurate observation, it is most 

 probable that this shght polar aggregation of the chromatin threads is to 

 be looked upon as the syuizesis which corresponds to that of the other 

 animals. 



DuESBERG ('08) denied the occurence of synizesis in the rat. Recently 

 Allen ('18) found a slight aggi'egation of the chromatin threads in this 

 animal, but his xiew is different fr.jm mine. He says : - " A vei-y slight 

 polar aggregation may occur during this period but no synizesis has been 

 observed with any method of fixation." Jordax ('14) rarely found the synizesis 

 occuring in the mouse, he says : " Thi3 is tentatively interpreted as synapsis 

 (polarized amphitene). If the nucleus is normal, as it appears to be, the 

 paired threads unmistakably indicate synapsis." 



As is the case in the horse and cattle, in this stage the nuclear wall 

 expands rapidly and soon apparently disintegr-ates (Fig. 130). During this 

 stage the parallel arrangement of the spiremes can not be seen at all (Figs. 

 16-18). With Aueebach's method the spii-emes take the same colour as in 

 the previous stage (Fig. 130). 



Most of the mitochondrial granules are usually grouped near the pole of 

 nucletis where the chromatin threads con^'erge, but none of them attach te 

 the nuclear wall (Fig. 16). 



Neither the nucleolus nor tho idiozome can be seen during this stage 

 (Fig. 130). 



The post-synaptic stage :— In the steige immediately following the synaptic 

 stage the chromatin threads gradually spread throughout the nucleus, becoming 

 more loosely situated (Figs. 18, 19). At the liegiuning of this stage some 

 spiremes appear to form an end-to-end arrangement which is regarded as an 

 indication of telosynapsis (Figs. 17, 18). In any case it is quiie certain that 

 in this stage the spiremes app?ar abaut half the original number, but they 

 do not increase in tUckuess, retaining their original form (Figs. 17, 18). From 

 this fact it is conceivable that the conjugation of chromosomes must have 

 taken place during the previous stage (synaptic stage\ Liter on the 

 chromatin tlu-eads elongate more and more until they resemble as those of 

 the hoi-so and cattle, while the outUne of tho nucleus becomes spherical and 

 more clearly defined (Fgs. 18, 19, 131). ^Yith Aderbach's method all the 



