DIVISION OF COLLAR-CELLS OF CLATHRINA COBIACEA. 625 



owino- to the fact that the uucleus is no lonsfer in its usual 

 position at the base of the cell, but has eitliei- migrated to the 

 apex ov has been preserved in the act of doing so, and is 

 found in some position between the base and the apex (figs. 

 1-5, etc.). Such cells are also characterised by being much 

 broader and stouter than the ordinary resting cells, but they 

 do not increase in height to an appreciable extent. 



By this process of migration the nucleus comes to lie 

 immediately under the blepharoplast, and at this stage a 

 curious appearance has been observed in two instances (figs. 

 4 and 5) ; the nucleus is seen to be flattened on the side 

 nearest to the blepharoplast, and from the blepharoplast itself 

 two streaks appear to radiate to the two ends of the flattened 

 side of the nucleus. Careful examination of each of these 

 preparations giv^es the impression that these two streaks are 

 in reality the optical section of a cone-shaped mass of proto- 

 plasmic substance, the base of which rests on the flattened 

 side of the nucleus, and which is, perhaps, the cause of the 

 flMttening. A comparison with the resting cell suggests that 

 tliis conical mass is derived from the peculiar vacuole with 

 granular contents, which was described in the last section as 

 situated in the direct line between nucleus and blepharoplast, 

 and that by the upward migration of the nucleus the vacuole 

 in question is pushed up until it is caught, so to speak, 

 between nucleus and blepharoplast, when, coming under the 

 influence of the forces of attraction or repulsion exerted by 

 the blepharoplast, it assumes the conical form seen. If this is 

 a correct interpretation of the phenomena, the vacuole should, 

 perhaps, be regarded as an archoplasmic vesicle, such as has 

 been described in other cases, and which supplies some part of 

 the material of the achromatic spindle in the mitosis. In fig. 4 

 it is seen that the flagellum is still present, though short, 

 while in fig. 5 the flagellum has entirely disappeared and the 

 blepharoplast has divided. 



The disappearance of the flagellum and the division of the 

 blepharoplast are two events Avhich take place independently 

 so far as their relative sequence in time is concerned, that is 



