190 Transactions of the Society. 



granular mass was presented, as seen in fig. 10. The granules 

 ^Yere more or less distinct, and were semi-opaque ; but the flagella 

 still were in active motion, and the whole mass was swirling and 

 swaying with irregular movement over the whole field. 



In earlier observations of this phenomenon, it was quite visible 

 that when it had reached this stage, the mass grew gradually less ; 

 but how was not so readily discoverable, because it was so slowly 

 effected. 



But by careful arrangement it was subsequently seen with com- 

 parative ease that it was, as it swam, dropping a stream of semi- 

 opaque gi'anules, by no means diflficult to see, as at a, b, fig. 16, 

 plate V. 



To study any changes that might happen in these was not 

 a matter of difficulty. 1 did it chiefly with the dry 1/35 ; but 

 where any points of special detail were to be made out I used the 

 oil lenses. 



The granules or sporules, or whatever we may call them, are 

 at first semi-opaque : but in the course of fifteen minutes they lose 

 this, and become transparent and highly refractive. Within a few 

 minutes from the assumption of this condition they are visibly 

 elongated, as at fig. 17, plate V. This elongation continues with 

 general enlargement as at fig. 18. In about an hour it has reached 

 the state shown at fig. 19, but it is very difficult to determine the 

 earliest appearance of the setae-like origins of the flagella which 

 begin to show themselves between the stages shown in figs. 19 

 and 20, but after this the progress is very rapid ; for in three hours 

 more the organism passes through the stages shown in figs. 19, 

 20, and 21, and in the last condition begins its earUest move- 

 ments ; and rapidly appropriating food as it moves, it reaches the 

 final condition shown in figs. 22 and 23, and was in several instances 

 followed into the process of fission, depicted in fig. 24, and which 

 constitutes a completing and re-entering of the life-cycle. 



To complete our knowledge concerning this form so far as could 

 be, I made, as in former cases, a series of experiments on the thermal 

 death-point of the germs. 



The apparatus 1 employed for this purpose is that which I 

 have before employed for the same purpose, and which I have 

 described, both to this and the Royal Society.* It enables an 

 examination of the immediately emitted germ to be subjected to 

 such thermal conditions, in fluid, as may be desired, and the germ 

 to be subsequently studied under any power, without the slightest 

 disturbance, and in normal conditions. 



From the nature of the spore-sac, and the slow mode of 



* See this Journal, iii. (1880) pp. 1-16, and Proc, Eoval Society, xxvii. 

 (1878) p. 332 et seq. 



