348 



Rev. W. H. Dallinger on 



[May 2, 



not at this time find more than this one ; bnt in the course of some 

 hours several more were present, perhaps as the result of fission. 



From this it appeared plain that the spores had survived a tempera- 

 ture of 220° F. in a fluid heat : but by a series of subsequent tests 

 conducted in precisely the same way, I found that if 220° F. might 

 not be considered the limit of temperature which the. spore could 

 survive, at least this organism never showed itself again after heating 

 the spore to 222° F. 



It thus appears that in this particular organism the dry heat is 

 considerably less destructive of the vitality of the spores than the 

 moist heat. That there is, indeed, a difference of 28° or 29° F. ; or, 

 speaking broadly, we might say 30° F. 



This is undoubtedly a difference of considerable importance. But a 

 temperature of 220° F. resisted successfully at all, implies of necessity 

 actual protection of some kind. I shall not attempt to theorize upon 

 or suggest what that may be ; but it is manifestly not beyond the 

 reach of chemical and physical science to approximate to an explana- 

 tion, whilst biological science furnishes analosy in higher and more 

 complex departments of its researches. One thing is absolutely 

 certain ; which is, that the optical condition of the freshly emitted 

 spore is quite distinct from that which it presents in from three- 

 quarters of an hour to an hour after development has commenced. It 

 is to the comparative opacity of the newly emitted germs that their 

 visibility at that time is due. Hence they are most certainly dis- 

 covered by means of a shaft of aln ost parallel light the of an 

 inch in diameter at right angles to the plane on which the spores are 

 lying, and their imperfect transmission of this reveals them. But in 

 the course of an hour they become far more transparent than even the 

 adult form. This is undoubtedly the result of the vital processes in- 

 volved in germination. The sarcode is in a fluid condition and cannot 

 resist the heat that surrounds it — a constant current of liquid must be 

 passing in and out of the sarcode by imbibition and exosmosis. The 

 result must be the circulation through the sarcode of fluid at a tempe- 

 rature destructive of the vital processes. Hence the destruction of 

 the adult at 142° F.. and there can be little doubt but the young 

 germinating form would be destroyed, for the same reasons, at the 

 same or — perhaps from the probably greater intensity of the vital 

 processes — even a lower temperature. But in the spore, the vital 

 activities of the developing protoplasm have not commenced; the 

 sarcode is in all probability in a fixed state ; and a protective condi- 

 tion of that sarcode, resisting the diffusion of heat through it, is by no 

 means difficult to understand. Indeed it will be palpably of service 

 to the organisms, and like desiccation enable them to overcome the 

 extreme vicissitudes of condition in temperature, drought, and so 

 forth, to which over the surface of the earth, they must, as septic 



