1897] NOTES AND COMMENTS 369 
above the average, and thus many Queens were early tempted from 
their winter quarters. Turning now to the numbers of wasps 
observed—in spring there were many ‘Queens’ to be seen, and 
many persons observed to me that we might expect a recurrence of 
the ‘ plague’ of 1893. This prediction was entirely falsified, for in 
all parts of the country wasps were conspicuously absent during 
August and September. My own observations on this point were 
conducted in Surrey, Hampshire, Norfolk, Hertfordshire, and Kent, 
and I am informed by friends that the same was noticeable in Scot- 
land, Lancashire, and Somersetshire. These facts seem to me 
sufficiently conclusive of the truth of my former conclusion, and I 
should esteem it a favour to be allowed to invite information from 
any of your readers whose experience may perhaps, during the past 
year, have furnished further evidence in the same or the opposite 
direction.” 
MODELS OF CELLS 
Pror, A. L. Herrera has recently published in the Memorias y 
Revista de la Sociedad Cientifica ‘ Antonio Alzate, Mexico, 1897, 
two interesting essays, in which he describes some attempts of his 
to make working models of the impact of forces upon cells and 
protoplasm. He points out that in the part of physiology dealing 
with the elaborate mechanisms of higher animals the construction 
of models, such as those to illustrate the flight of insects or the 
action of the valves of the heart, has been useful; and he attempts 
to apply the same principle to the fundamental phenomena of 
protoplasm. To a certain extent he has been anticipated by 
Biitschli and others, and we are bound to admit that his working 
models are of coarser texture and apparently less adapted to the 
delicate reaction of protoplasm than the oil foams of his predeces- 
sors. None the less, many of his experiments are interesting and 
ingenious, and may serve a useful purpose in kindergarten science. 
In the first essay, entitled ‘ Los Infusorios Artificiales,’ he tries to 
explain vibratile movements of cilia by means of elastic tubes con- 
taining diffusible liquids and placed in other liquids. His idea 
appears to be that osmosis currents between protoplasm and water 
and the stresses produced in the elastic cell-wall set up the vibra- 
tions. In the second essay, written in French, he describes a series 
of experiments showing the reaction of elastic spherical bodies to 
pressure by the elastic surfaces. He obtained a number of results 
strikingly resembling known animal and plant forms. We com- 
mend his essays to the curious. 
