176 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



also be observed that the nucleolus still persists, which 

 shows that it has not been used to form the central network. 

 This is the latest stage in which the nucleolus was seen, 

 but what eventually becomes of it was not observed. 



In the next figure we have a characteristic multipolar 

 spindle. Here the ^bres are straight and form cones which 

 terminate in sharp points. We see extending from the 

 apices of the cones fibres which have free ends. These 

 fibres eventually become the mantle-fibres which are so 

 characteristic of the mature spindle. 



The multipolar figure becomes bipolar by the fusion of 

 the cones in much the same manner as it does in Equisetum, 

 as shown in figs. 14 and 15, but during the process the 

 mantle-fibres have developed to a considerable length. 



From the time of the breaking down of the nuclear wall 

 the chromosomes have been in connection with the network 

 from which are developed the spindle-fibres; so that this 

 process differs materially from those cases where the 

 spindle-fibres have been described as growing in and 

 becoming attached to the chromosomes. 



As shown in figs. 15 and 16, the mature spindle termi- 

 nates in sharp points ; there are three kinds of fibres present : 

 The contractile fibres, which are in connection with the 

 chromosomes, are compound in nature, being made up of a 

 number of fine fibres. The continuous fibres extend from 

 pole to pole uninterrupted. The mantle-fibres are remark- 

 able for their great length and early development; they 

 consist of very delicate straight threads; those from one 

 pole cross those from the opposite pole in the manner 

 shown in figs. 15 and 16. It should be observed that 

 although the mantle-fibres are of great length they never 

 extend beyond the perikaryoplasm. 



After the mantle-fibres have reached their maximum 

 development the contractile fibres commence to draw the 

 chromosomes to the poles. This takes place in the usual 

 way. It will be noticed, however, as shown in fig. 17, that 

 during this process the mantle-fibres appear more divergent 

 from their respective poles. When the chromosomes have 



