1904 ] BRIEFER ARTICLES 65 
what in P. decipiens becomes a very well marked four-rayed figure. I 
observe he does not figure centrosomes or centrospheres, such as are 
easily seen at the corresponding stage in Aneura or Fossombronia. [| 
fancy these bodies are not always identically developed, perhaps even 
in closely related forms. I have become convinced that in many liver- 
worts there are often present within the’centrosphere, where it can be 
distinguished, one or more particles that may be looked on as repre- 
senting a centrosome. The number is, I think, of no great moment. 
The existence of the swéstance, whether in one or more granules, is the 
essential point. A nucleolus does not cease to be a nucleolus because 
several of them may be present in a nucleus which more frequently only 
contains a single one, and the same argument applies, I think, to the 
centrosome substance where it can be identified at all. 
And as to the quadripolar spindle, whether we choose to restrict the 
term “spindle” to that portion of the achromatic apparatus that has 
become continuous from pole to pole, or whether we prefer to extend 
it so as to include the fibers or substances that are differentiated between 
the centrospheres and the nucieus during the prophase, irrespective as 
to whether these retain their positions later or not, is a matter of indi- 
vidual taste. Personally, seeing that they form a stage in the differ- 
entiation of the interpolar spindle (with or without fusion in pairs or 
otherwise), I embrace the latter alternative; and so include the four- 
rayed figure, independently of its degree of development or permanence 
as part of the spindle apparatus. I do not think much is gained by 
limiting the term “spindle” to the later stages, or restricting it purely to 
bipolar forms. 
I should like to take this opportunity of correcting a statement in 
the memoir on nuclear division to which I have already referred in this 
note. Atthe time that paper was written the terms “heterotype” and 
“homotype” had not acquired that definite meaning that now attaches 
to them. At the present time I should certainly not regard the second 
division of the spore mother-cell as in any case in essential characters 
being really of a heterotype nature. The small size of the objects 
makes an exact appreciation of their evolution and final form a mat- 
ter of some difficulty. I have, however, no reason to suppose that 
those few instances in which a renewed examination of the question has 
not resulted in definitely settling their homotype character, do really 
in any way differ in this respect from the many forms in which 
the nature of the second mitosis can be satisfactorily ascertained.— 
J. B. Farmer, London, England. 
