I02 GARDINER. [Vol. XV. 



centrosome, while the other portions of the amphiaster are 

 not markedly over-stained. When, however, the color is prop- 

 erly drawn the centreole is tinged a faint blue, as is shown in 

 Fig. 36. There are at this stage a few faint, dark fibers which 

 radiate into the surrounding centrosphere from the centreole. 

 By the time the chromosomes are fully formed, these radiations 

 are exceedingly distinct (Fig. 31), but from this stage on they 

 begin to fade away. Also as the radiations fade the cen- 

 trosome enlarges so as almost to fill the centreole, and at 

 the same time it elongates in a direction at right angles to the 

 long axis of the spindle. This elongation occurs at about the 

 time the equatorial plate is completely formed. Figs. 3 1 and 

 34 being portions of the same amphiaster. I believe this is 

 the stage at which the ova are normally laid, for the anaphase 

 does not occur until after oviposition. 



It is, however, not unusual to find a centrosome, as shown 

 in Fig. 32, apparently consisting of numerous fine granules 

 which stain very deeply ; also where it is exceedingly indis- 

 tinct, as in Fig. 33, although I have found no sections through 

 fully formed spindles when it is altogether absent. It is 

 noticeable that in these cases the whole spindle is somewhat 

 indistinct in outline, and I believe is undergoing the retro- 

 grade development described in p. "jj. The large number of 

 cases cited by Wilson (13) and others, in which the centrosome 

 is shown to be a permanent organ of the cell, presents a curi- 

 ous contrast to its action in this ovum. The small body 

 shown in Fig. 9, which for want of a better name I have 

 called the archoplasmic vesicle, may be permanent, but the 

 spot within it, the centrosome, is not, unless its chemistry so 

 changes that it answers to a stain at one time and not at 

 another. It should be borne in mind that these studies are 

 made on different series hardened in sublimate, sublimo-acetic, 

 Hermann's and Flemming's fluids, and in no case have I found 

 any trace of a centrosome except when the spindle is well 

 advanced in its formation. 



