1878.] the Life-History of a Minute Septic Organism. 349 



organisms, be exposed. But from a series of experiments on the spore 

 of such of the " monads " whose Life- Histories were worked out by 

 Dr. Drysdale and myself, as I have been enabled to get again during 

 the last two years, I have been able to satisfy myself that 30° F. is by 

 no means the fixed difference between the power of thermal resistance 

 possessed by the spores of these forms when heated in a dry and a 

 moist condition. There is considerable variety in this matter, and 

 variety which in all probability, nothing but a perfect acquaintance 

 with the vicissitudes through which by adaptation they have survived 

 in their evolutional history, could explain. 



In conclusion, without entering into details, I may observe that 

 these forms have, as far as my observations have extended, a far 

 greater capacity to resist heat than the bacteria; but their distribution 

 is far more limited. 



DESCRIPTION OF PLATES. 

 Piates 8 and 9. 



Figure 1. The normal form of the organism described; d being the nucleus. 



Figure 2. The representation of the mode in which it appears by mechanical means 

 to break up the decomposing tissues of the animal matter in the macera- 

 tion, a, b, are points at which its lateral flagella are " anchored ;" it then 

 draws its body down, coiling the flagella into spirals seen at c ; it then 

 springs up and forward in the direction of the arrow d, and with the 

 flagella as a radius darts rapidly down upon a piece of tissue in the arc of 

 a circle shown by the arrow e. 



Figure 3. The first indications of fission are seen at a, b, and the nucleus has 

 moved to the centre. 



Figure 4. Fission is in progress as seen at a and c, and in the nucleus b. 



Figure 5. It is still progressing ; a pale line runs through the dividing body, and the 

 nucleus has separated. 



Figure 6. Fission still further advanced. 



Figure 7. Only a neck of sarcode now unites the bodies ; this is sharply pulled, and 

 results in a thin fibre connecting two forms as seen in fig. 8. 



Figure 9. This has stretched as here drawn ; the bodies pulling in the direction of 

 the arrows, until the fibre snaps in the middle, and two perfect forms go 

 free. 



Figure 10. At the terminus of a series of fissions in about a third of the cases, the 

 body becomes changed, slow of movement, and amoeboid, as here drawn : 

 and then rapidly changes into the shape seen in fig. 11. 



Figure 12. The form shown at fig. 11, after forming a band seen at a goes into the 

 midst of a group in the " springing " state, and speedily unites itself to 

 one, which at once goes free ; and they swim together as in this figure. 



Figures 13, 14, 15, 16, 17. Represent different progressive stages of fusion, which 

 terminate in a still sac (15), which ultimately opens and pours out spores 

 (16,17). 



Figures 18 — 25. Different progressive stages in the growth of the emitted spores. 



Figure 26. A piece of glass apparatus for testing the thermal death-point of the 

 adult, and for discovering whether or not the boiling-point in a fluid 

 destroys the germ. The cell c enables this to be determined by micro- 



2 a 2 



