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



along its periphery; these begin to stain violet with the 

 Flemming triple stain. At the same time a few delicate 

 fibres are seen along its periphery, which resemble the 

 granules in their manner of staining; they seem, in fact, to 

 be composed largely of granules of the same sort as those 

 just described. 



2. Genetic Stage. 



The granules in the periphery of the layer increase in 

 number and size and stain deeper and deeper violet, as is 

 seen in figs. 3 and 4. Eventually they become densely 

 crowded, and apparently fuse to form an unbroken line 

 which stains deep violet. Careful focussing shows that 

 this line represents sooner or later a continuous membrane 

 which forms a complete and unbroken investment of the 

 spindle during its formation, and which will therefore be 

 called the sf indie wall. The spindle wall is very often, at 

 least in the early stages, not in contact with the nuclear 

 wall, but in many cases it coalesces at one or more places 

 with the nuclear wall. This may happen even in the ear- 

 liest stages, as is shown in fig. 2. 



During the formation of the spindle wall there are grad- 

 ually developed, between it and the nuclear wall, radial 

 fibres such as are seen in fig. 4. These fibres are at first 

 very delicate, stain faintly orange, and contain irregular 

 scattered granules, which tend to stain violet. As the 

 formation of the spindle wall progresses, the granules 

 increase in number and size, become crowded, and finally 

 seem to fuse to produce continuous violet fibres. There- 

 upon the fibres lose their granular appearance, become 

 thicker, straighter, and stain more and more violet, as is 

 shown in figs. 5-8. Inasmuch as these fibres subsequently 

 form the spindle, they will be called the, genetic fib7'cs ; the 

 layer containing them, i. e., the space between the nuclear 

 and spindle wall, will be called the genetic layer, and it is 

 suggested that this term be used generally to designate the 

 layer containing the genetic fibres, whether that layer be 

 bounded by a definite wall or not; the stage which is 



