No. 3-] BIOLOGY OF THE STENTORS. 537 



equally frequent bipartitions that I have observed accurately, 

 has the size of the original progenitor been maintained. After 

 only two or three consecutive fissions at 24-hours' interval, the 

 reduced dimensions of the offspring become very noticeable. 

 I believe the cause to be a lack of sufficient time between the 

 bipartitions for the offspring to attain the size of the parent, 

 and consequently after the next bipartition the grand-children, 

 so to speak, are only a little over a fourth the size of the 

 grand-parent, whereas they should normally be half its size. 

 As the culture described above had undergone the most rapid 

 multiplication, its members were reduced to the most minute 

 dimensions. They became mere dwarfs, measuring at the 7th 

 bipartition only .630 mm. (extended) by .285 mm.,^ and were 

 rapidly passing into a lethargic condition. 



On Dec. 16 they were again examined. I had repeated the 

 observation made by Maupas — that inability to take food did 

 not altogether prevent fission ; but such fission was of course 

 not followed by any growth of the offspring, and therefore 

 produced a rapid reduction in size. The few Stentors still 

 living were in a moribund state. The movement of the 

 membranellae was hardly perceptible. In most instances the 

 mouth parts were nearly or wholly atrophied. The average 

 size was .450 mm. in length, and .120 mm. across the frontal 

 field. On staining specimens with methyl-green, I found the 

 nodes of the meganucleus only 5-10 in number, and much 

 reduced in size, although still very large in proportion to the 

 size of the animal, which consequently possessed an abnormally 

 large amount of nuclear substance in proportion to the cyto- 

 plasm. The nuclein took as deep a stain as usual. 



My most successful culture was made in a large watch-glass 

 kept supplied with fresh water to make good that lost by 

 evaporation, not over-supplied with food {Glaucotna scintillans) 

 and furnished with minute green algae, which grew freely and 

 kept the water well oxygenated. The temperature was variable, 

 falling to I2°-I5° C. at night, and rising to 22° during the day. 

 The record is as follows : — 



1 The normal size of the species, it will be remembered, is 2 mm. by .5 mm. 



