314 
ona large number of individuals, I cannot place on record a 
single instance of clear and unmistakable scorpion suicide. 
Rondebosch, January 1 C. LtoyD MorGAN 
Mimicry in Moths 
I HAVE read with great interest the observations of the Duke 
of Argyll on Mimicry in Moths. I remember more than one 
similar occurrence during my travels. The most curious was 
as follows :— 
Whilst in Japan, a messmate brought on board, in an 
ordinary po’, a beautiful trained shrub with a leaf much 
resembling that of an orange. It was placed on the ward room 
table where we all sat, the steward removed it from the table to 
the top of an harmonium at least three times a day, and I 
watered it when required, and often examined.and admired it ; 
in about eight or ten days it began to show signs of failing ; 
and, thinking it might be infected with spider or green fly, I 
examined it carefully, and in doing so I disturbed a large green 
smooth-skinned caterpillar. Like all animals on board ship he 
soon became a great favourite, and we often asked strangers to 
point him out and in no case did they succeed. 
He always lay along the edge of the leaf, with his head to the 
point and eat at each bite, exactly the breadth necessary to pre- 
serve the contour of the leaf as far as possible, when he reached 
the point, by a few sharp convulsions he returned to the stem 
and began another row. Whenhe had finished one half of the 
leaf he began the other; and when nothing but the centre rib of 
the leaf was left he eat backwards along the stem. He was the 
most economical feeder I ever saw, only a very little bit of the 
centre rib of the leaf was bitten off and fell to the ground, and 
the hard stem of the leaf was left. 
I soon observed that he could assume the exact shade of the 
leaf he was feeding on, and I frequently shifted him and watched 
the process. 
In due time he assumed the chrysalis form; he partly sus- 
pended, partly glued, himself to the stem of the plant and it 
was very difficult to detect him; but not nearly so difficult as in 
the caterpillar state. 
He remained a very short time in the pupa, and one day I 
was called by a-messmate who informed me that ‘‘ My beastly bug 
had hatched out,” and at first I thought this was the case, as a 
beautiful black and gold butterfly was expanding his wings and 
legs on the table, and soon took wing, but was captured and 
handed over to our buz collector, who by the way took no 
interest whatever in the prior stages ; he was neither butterfly, 
moth, nor beetle, so nothing to him. 
I went to observe how he had broken out of the sheath and 
was astonished to find that my chrysalis was safe and sound, the 
butterfly we had certainly did not come from it. Then where 
did it come from? We were still in Yokohama harbour, and it 
was a common occurrence that insects flew off to the ships. 
But how did a butterfly in the state I saw this one get on the 
ward room table? I came to the conclusion that the pupa had 
been attached to the plant or pot; I did not anticipate what 
took place. Ina few days another butterfly, to all appearance 
the brother of the first one, was seen (but not by me), to emerge 
from the chrysalis we had at first observed; and I have no 
doubt the first insect had eluded all our prying, and that there 
were two caterpillars all the time on the plant. 
I do not get NATURE until it isa fortnight old, and I have 
waited with anxiety to see if any one better able than I am would 
endeavour to show that mere physical causation is sufficient to 
account for all the phenomena disclosed by the Duke's admirable 
observation of the moth. 
I look upon the Duke as one of the best observers of Nature 
we haye, and his opinions must carry great weight ; and believing 
as I do that in the Theory of Natural Selection the future exist- 
ence of our race and all hope of advancement in morality is 
bound up, Iam anxious that his doubts on this subject should 
not carry weight with others. 
I think the whole question lies in this—were either of these 
caterpillars, or the Duke’s moth perfect, or even the most perfect 
of their kind ? 
I believe Ihave had more opportunity of observing cases of 
mimicry than his Grace has, and I have always found that the 
individuals vary as much in these forms of life as in any other. 
At Labuan one of the Engineers of the coal works sent a native 
out andin half an hour he returned with seven leaf-insects. I 
had picked one up in my walk from the settlement, and although 
at first each appeared a perfect leaf to my eye, I soon found 
NATURE 
[ Fed. 1, 1883 
great differences between the individuals; some being much 
better specimens than others—just as all sheep are not sheepish 
to the shepherd—and I think it is quite possible that not one of 
these eight insects would deceive the eye of an average natural 
enemy. Let us suppose that anyone of these were so perfect as 
a mimic, that it would deceive this enemy, it might be wanting in 
the advantage of perfect rest whilst under inspection, and thus 
be detected. It was by the movement of the insect that I was 
enabled to get the one I picked up. The Duke’s moth was 
betrayed by his ‘‘ beaded eyes and thorax ;” and last of all, 
there was a small hole in the covering of the bright wings, which 
the Duke considers one of the mysteries of nature, and through 
all the mimicry of this moth the Duke with very little trouble 
detects the imposter ; as far as he was concerned, all the effort 
of nature was wasted. If I may be allowed the paradox, it is 
only when one has come to see what a botch nature has made of 
its work that its beauties can be properly appreciated. I admire 
quite as much the quickness of eye that belongs to the lizard 
that may have been on the watch to capture the moth ; these 
‘‘mysteries ” have gone on together ; and wheie a moth ora 
lizard failed ever so little it went down whilst its better appointed 
brother was the fittest to survive. Until the mind has taken in 
how constant the battle is, how small the advantages must be 
when the enemy is travelling the same path, it is difficult to 
resist the feeling of wonder and the desire to account for all by 
a fat of creation. 
I remember some remarks by the Duke of Argyll in a similar 
strain, when he observed three water-oozels take the water for the 
first time. He was struck with the way in which they all dived 
and swam, so perfectly ; but I think he failed to consider this 
view of the matter—did any one of these surpass the others in 
the art, even were his advantage so little that the Duke was 
unable to detect it? if so, then provided he was equal of his 
brothers in all other respects, he was the fittest to survive ; and 
as we evolutionists only claim little by little ; its ordinary phrases 
are no lean and empty formula to me. 
Nothing but the conviction that, in the new light thrown on 
nature by Charles Darwin and his numerous disciples, lies the 
happiness or misery of our race, would have emboldened me, 
so indifferently educated for the task, to take up the subject 
and your time. DUNCAN STEWART 
Knockrioch, January 25 
Clerk-Maxwell on Stress 
CAN any of your readers give me a reference to the note in 
which Maxwell, commenting on or replying to a correspondent 
of Nature, gave his ideas as to the nature of stress in a beam 
or cord ? Ate 
The Comet 
May Task space to make some observations about the orbit of 
the Great Comet of 1882? 
Looking on the many elements pnblished in NATURE, in the 
Dunecht Circulars, and in the Astronomische Nachrichten, 1 find 
very great differences between one and another. Especially the 
elliptical elements calculated by Mr. S. C. Chandler, Mr. Frisby, 
Mr. Kreutz, and Mr. Morrison present periods peculiarly 
different. 
Now this fact can be produced 1ut by two causes ; either it may 
be that the different observers considered different parts of the 
nucleus as the brightest part; or it may be that the movement 
of the comet has been much perturbed by some bodies of the 
solar system. 
The first hypothesis is very probable, as you remark in the 
“ Astronomical Column” in NATURE, vol. xxvil. p. 300. 
The division of the head in two, and perhaps three portions, 
is a fact well observed by many astronomers, and well shown in 
the drawings published by Mr. A. A. Common, Dr. Doberck, 
and Mr. W. T, Sampson in NATuRE, vol. xxvii, pp. 109, 129, 
and 150. 
But I observed that with small magnifying power the appear- 
ances of the brightest part of the head maintained always a 
certain unity, which would not admit great mistakes in the 
observations. Therefore it stems to me that, unless we suppose 
considerable and unknown variations in the form of the nucleus, 
only the difference of appreciation of the point observed can 
hardly explain such a great, and I say regular, difference between 
one orbit and another. 
I say regular difference, because I remark a certain peculiarity. 
