890 SUMMARY OF CURRENT RESEARCHES RELATING TO 



their tiny weight. The rotifers usually made their way to the 

 Volvoces within the parent, where they appeared to take up their 

 quarters. The next thing noted was that when Volvox was placed 

 upon white blotting paper, which of course left them high and dry, 

 they still retained a good deal of their rotundity, and became flattened 

 much less than would be expected if they were really hollow. 



However, a little experiment, which it is easy for every one to try, 

 shows that Volvox is without any cavity whatever, and that the 

 perfectly transparent contents of the globe appear to possess little, if 

 any less firmness than the pellicle or membrane which forms its peri- 

 phery. This may be shown by taking Volvox in good quantity and 

 straining the water from them ; by this means a little mass may be 

 obtained. Let the Volvoces thus collected be taken up rather roughly 

 by means of a syringe, and placed in water containing carmine or any 

 fine solid matter. It will probably be found that some of the Volvoces 

 have been broken, some perhaps even into fragments which still 

 display the rolling motion. Now, if little care is used in examining 

 the ruptured specimens, it will be seen that the carmine adheres to 

 any surface thus exposed, at once displaying the fact of its solid 

 consistency. This is much more easily observed if the Volvoces 

 are again strained off and placed in a compressor with a little clean 

 water. 



With this elucidation it is no longer difficult to understand how, as 

 the young Volvoces continue their growth within the parent, there 

 comes a time when the overstrained envelope bursts, and, as before 

 remarked, they escape with so much energy. The manner and means 

 of escape of the young are often seen in a gathering of mature speci- 

 mens, especially if the weather is fine and warm, but this result may 

 be brought about much sooner by the addition of a little carbolic acid, 

 which will often cause nearly every one to burst within a very short 

 space of time : a fact I have noted to my chagrin when mounting slides 

 of this beautiful organism. 



Solid is too strong a word, perhaps, to apply to matter which can- 

 not be more than gelatinous, and is here used only in antagonism to 

 the word hollow ; but, if the spheres be stripped of their outer green 

 covering, this envelope collapses, while the contents retain their 

 spherical form, as is readily seen by the displacement of the 

 carmine." 



Further remarks subsequently added by the author are as 

 follows : — 



" Since I read this note, which necessarily caused much discussion 

 at the time, it has been confirmed by several observers, and, as it has 

 not been published, is introduced here. 



I have tried the further experiment of freezing a mass of Volvox 

 upon a slide, and with a sharp knife cutting some sections, which 

 were found to retain the matter within the green envelope, and this 

 internal matter, whatever it may be, proved to be sufficiently dense to 

 support particles of carmine, dirt, or any other solid matter which 

 lodged upon it. 



The contents are so perfectly colourless that they are quite imper- 



