198 Transactions of the Society. 



But during this time I began to discover a renewed tendency to 

 vacuolation. Jn this instance it commenced in very minute vacuoles, and 

 they were sparsely distributed, but in each of the three monads steadily 

 increased in number, but did not, as in the former instance, fuse into 

 larger vacuoles, but only increased in number. In figs. 16, 18, 20, 

 are drawings of M. DalUngeri, D. DrysdaU, and T. rostratus, as they 

 were in the fourth month with a static temperature of 93°, while figs. 

 17, 19, 21, show corresponding organisms at the end of the fifth month, 

 under the same circumstances. This represents the extreme state of 

 vacuolation attained, and at the end of the ninth month, and not until 

 then, was I able to elevate the temperature of the fluid a degree. But 

 in the course of three weeks at 94° they became perfectly normal, lost all 

 trace of vacuolation, and were most active and prolific, and submitted 

 without great inconvenience to an elevation of temperature up to 102^ in 

 fourteen weeks. 



After this there was a slightly increasing difficulty until I reached 

 107° which took two months, and there another pause ensued. During 

 the next three months a relatively slight vacuolation took place, and 

 permitted a further addition to the temperature until after seven months 

 more, with smooth careful progress I reached 137°. 



This appeared to be a very critical point, for directly the 136th 

 degree had been passed there were symptoms of oppression and distress, 

 and on touching 137° this was very manifest. 



I was compelled to play the thermal point back and forward for 

 three weeks before there was an approach to normal activity and 

 fecundity, but beyond this point I dared not advance. 



In putting a drop, for example, upon a thermal stage, at the point 

 136°, and then elevating it slowly through 137° to 138^, torpor became 

 universal in all the three organisms in the field. 



My only hope of further advance was in patience. 



After six months of constant and careful endeavour, not the slightest 

 advance appeared to be made. There was no greater readiness than 

 before, and I began to despair of further success, no vacuolation or any 

 other feature that could be noted was discoverable. In this way I 

 continued the observations, with constant test experiments for twelve 

 months, and with no apparent advance. 



But at the end of this time I saw that a slight tendency to endurance 

 of a minute elevation towards 138° was visible, and with it a rapidly 

 increasing growth of vacuoles, which spread as before through the sarcode 

 of each of the three forms, but the tendency was for these to pass from 

 small into large vacuolations. In a month these were universal, and in 

 figs. 22, 23, 24, 25, I have drawn successive stages of this condition, as 

 they appeared in one month from the beginning of the process. 



During this time I had been able to raise the temperature 4°, and 

 the vacuolation disappeared rapidly. The progress was now as rapid as 

 it had been slow previously, and admitted of as much as 2° elevation 

 at a time, and without further difficulty I slowly progressed to 150°, 

 more slowly to 155°, and was again brought to a dead standstill at 

 158°. 



Here, with such pain as I presume is natural, I have to close the 



