628 L. R. Cary. 



To give an idea of their diameter it may be said that in any cell 

 each fibre was of about the same diameter as tlie centrosome in 

 the same nucleus. 



In the anaphase of the division the chromosomes are drawn 

 apart, from the equatorial plate, each daughter plate converging 

 toward the centrosome at the corresponding side of the nucleus. At 

 the beginning of this process the nucleus still retains its nearly 

 spherical shape: but in later stages, when the chromosomes have 

 been drawn up close to the centrosomes. the outline of the nucleus 

 becomes elliptical. The long axis of the ellipse corresponds with that 

 of the mitotic figure. 



At about this stage (when the daughter chromosomes are 

 gathered in a mass near the centrosomes, and those in the centre 

 of the mass have begun to lose their identitj^) there is the beginning 

 of a constriction about the middle of the nucleus. This constriction 

 seems to take place rather slowly, to judge from the correlation 

 between the stages in the constriction of the nucleus and the 

 condition of the mass of daughter chromosomes found in each of its ends. 



On one occasion a division was observed to take place in a 

 living sporoc3'st which 1 was studying. When this nucleus was 

 first observed (it is impossible to state with certainty whether or 

 not it was a germ cell, although its location at the broad end of 

 the sporocyst as well as its large size would make this inference 

 seem probable) it was spherical in shape, and differed in no 

 appreciable respect from the nuclei surrounding it. When noticed 

 again it had become considerably^ elongated and there was a slight 

 constriction about its middle part. For the remainder of the time 

 until the complete separation of the daughter nuclei, this nucleus 

 was constantly under observation. My notes show that from the 

 time when it was first noticed that this nucleus was different from 

 the others, until the time when the daughter nuclei had separated, 

 a period of twenty minutes had elapsed. 



As seen under the comparatively low magnification used, all 

 that could be observed was that the constriction became gradually 

 deeper and deeper until finally the nucleus became separated into 

 two parts. The whole cycle of events resembled an amitotic division 

 which, indeed, at the time I considered it to be. 



The study of sections of preserved material has shown, however, 

 that the facts above recorded are of normal occurence during the 

 mitosis in this trematode. 



