STRUCTURE AND LIFE-HISTORY OF VOLVOX GLOBATOR. 233 



ON THE STEUCTURE AND LIFE-HISTORY OF 

 VOLVOX GLOBATOR. 



BY A. W. WILLS, F.C.S. 



(Continued from page 214. ) 



We must now revert to the minute structure of the mature parent- 

 sphere, which has been exhaustively studied by Cohn, Busk, and 

 Williamson. 



In the outset it should be stated that the last-named observer 

 believes that there are two distinct forms of Volvox, in one of which the 

 peculiar structure which I am about to describe exists, while it is 

 absent from the other. Busk disputed the the accuracy of Williamson's 

 observations on this point, but, in an appendix published subsequent to 

 the body of his essay, he states that he has detected this same structure 

 in specimens from Manchester, but not in his own. 



I have failed to develop it by the means recommended by Williamson, 

 but have succeeded in making it evident enough in a great number of 

 specimens from Sutton, by the use of other re-agents, and especially 

 by the application of aniline purple, an invaluable auxiliary in the 

 examination of minute vegetable cell-structures. 



This substance stains the protoplasmic elements of such structures 

 to a colour which appears deep purple by direct light, and crimson by 

 dark back-ground illumination, and reveals details which are wholly 

 invisible without its use. 



The colour is, however, greedily absorbed by some of the materials 

 used by the microscopist, so that a judicious choice of these is necessary 

 to ensure success. Objects stained in this manner are, for instance, 

 rapidly bleached if mounted in gold size cells, and I have for the 

 present adopted zinc-white in its place. Among other re-agents which I 

 have used are eosin, iodine, iodised glycerine, carmine solution, 

 potassium permanganate, nitrate of silver, and other salts, some of 

 which bring into view various parts of the minute structure of plants ; 

 but aniline colours, applied with due precautions, produce the most 

 rapid and striking effect. 



Refekences to Plate VLTI. 



[The figures in this plate are drawn from a paper by A. W. Bennett, Popular 

 Science Review, July, 1878.] 



Fig. 1.— Monoecious Colony of Volvox. showing a, a% Antheridia ; a3, Anthero- 



zoids ; b,62, Gynogonidia; M, bi, Oospheres. 

 Fig. 2. — Complete Antheridium. 

 Fig. 3.— Oosphere penetrated by Antherozoids. 

 Fig. i.— Fertilised Oo-sphere, or Oo-spore. 

 Figs. 5, 6.— Antherozoids. 



AA 



