14 Transactions of the Society. 



Another (" Biflagellate," vide Fig. 9) also resisted by its germs 

 250° Falir. in dry heat, but could only survive 232^ Fahr. in the 

 fluid heat. 



One of the forms (" Cerco-monad," vide Fig. 7) which could 

 survive 260° Fahr. dry heat, was destroyed at 238° Fahr. in fluid 

 heat. 



There were two that could just survive 300° Fahr. in the dry 

 heat, viz. the one (" Uniflagellate," Fig. 11) concerning which the 

 details of these experiments have been given ; and the " Springing 

 Monad" (Fig. 10). These were destroyed in fluid at 268° Fahr. 

 and 252° Fahr. respectively. 



One other remains (the "Hooked Monad," Fig. 8). In this 

 form, however, the emitted contents of the sac were in an active 

 condition — moving freely, in fact. These survived exposure to a 

 temperature of 180° Fahr. in air, but were wholly destroyed at 

 150° Fahr. in fluid. 



To these may be added the results of investigations made by me 

 on a new form and published last year in the ' Proceedings ' of the 

 Royal Society.* In air its limit of temperature for the spores was 

 250° Fahr. In fluid heat they were wholly devitalized between 

 220° Fahr. and 222° Fahr. 



Averaging these results, then, and taking the mean death-point 

 by heat for the mature form as 140° Fahr., we find the mean heat- 

 resisting power of the seven monads, by means of their spores, to 

 be greater than the resistance possessed by the adult, in dry heat, 

 as 1 to 1'82 or nearly as 5 to 9 ; in heat endured as a fluid, 

 as 1 to 1'6 or 5 to 8 ; while the average difference of the destruc- 

 tiveness of heat in air and heat in fluid is as • 87 to 1 or nearly 

 9 to 10. 



On these facts it may be remarked : — 



1. That the six (out of these seven) monads, that produced spores 

 proper, whose spores, speaking generally, were the smallest, were 

 the best able to survive the heat conditions imposed. Indeed the 

 one that poured out spores invisible until growth had made them 

 large enough to be seen, not only reached the highest temperature, 

 but resisted it more efficiently than the other which just survived 

 this temperature, but whose spores, though seen with great 

 difiiculty, were yet much more easily seen. 



It is noticeable that the spores of both these were ejected from 

 the sac in what appeared hke a glairy fluid. 



But the monad (Fig. 12) whose spore was just devitalized at the 

 boiling-point of water, was the largest of the group, and produced 

 the largest spores — easily discoverable with 1800 diameters — and 

 they were not interfused with a glairy fluid, but ejected as simple 

 masses of spores, which rolled over the field. 



* No. 187. 



