340 



Rev. W. H. Dallinger on 



[May 2, 



fifteen minutes, but certainly -within an hour, the first signs of fission 

 would show themselves, as indicated in a, b, c, d, fig. 25 ; and from that 

 time fission, in successively separated individuals, continued in active 

 progress for hours, as before described. 



Thus the life- cycle was completely made out. 



It may be noticed : — 



1. That the method of fission is both delicate and complex, being 

 not merely a separation into two parts of a particle of living proto- 

 plasm, but a division of distinct organs, such as nucleus and flagellum. 



2. That the transformation of the individual form, at the terminus 

 of a series of fissions, into an apparently new organism, prior to genetic 

 blending (as shown in figs. 10, 11, Plate 8), is remarkable. And 



3. That the life-cycle of this form is rigid, and marked by no caprice. 

 It passes regularly through the same metamorphoses. If seen in any 

 given state, it could be positively affirmed through what stages it had 

 passed, and through what remaining stages it must subsequently pass, 

 to reach the adult condition. 



It now remained to determine whether the spore, or germinal par- 

 ticles, emitted by the sac, possessed any capacity to resist the action of 

 heat not possessed by the fully developed form. 



It was first carefully determined, by a method to be presently de- 

 scribed, that the adult organism never survived after exposure for five 

 minutes to a temperature of 142° F. 



For determining the amount of heat resistance possessed by this 

 spore, two methods were employed : — 



1. The ordinary three by one inch slips of glass, used for micro- 

 scopical purposes, were cut into three pieces, each of which was thus an 

 inch square. These could be put into and worked with the " continuous 

 stage." The septic fluid containing the organism was placed upon it, and 

 covered in the usual way with the thinnest covering glass. It was then 

 watched with suitable lenses until, either in that or in some successive 

 drop of the fluid, a cyst was seen to pour out its spores, as in fig. 16, 

 Plate 9. It was then at once taken and placed in a small brass 

 chamber, into the middle of which the bulb of a delicate thermometer 

 was fixed, the tube fitting air-tight into the cover of the chamber, and 

 the expansion of the mercury being read off outside. 



The small square of glass containing the fluid and spores was placed, 

 as it came from the stage of the microscope, in the middle of the 

 chamber. The chamber was then closed, and heat so applied as to 

 slowly raise the temperature of the air within. In half an hour it had 

 reached the temperature I desired, which was 210° P. ; and the chamber 

 was kept accurately at this point for ten minutes. 



The square of glass was then taken out, cooled, and examined, and, 

 of course, to the lens presented a dry amorphous aspect. 



Previously some of the fine capillary tubes known as " vaccine tubes " 



