el 
remarkable African affinity’ in the Lepidoptera of Aus- 
tralia, in reference to the case of the larva of Loratophora 
vuinerans Lewin, The instances which he cites as analo- 
gous, however, are very different in character, for he 
quotes the mention by Livingstone ‘of a caterpillar called 
Rigura, producing fearful agony if a sore is touched wth 
zts entrails’; and the statement made by Baynes and 
other travellers, that a caterpillar is used by the Bushmen 
to poison their arrows. It is evident that, if a caterpillar 
be used at all for poisoning arrows (concerning which 
report my inquiries have hitherto been attended by no 
satisfactory result) it must be the intestines or juices of 
the animal which are so employed. But the case of 
Doratifera vulnerans is the common one of (what appears 
to be mechanical) irritation, by means of clusters of 
spines, a defence possessed by many caterpillars, not only 
in Australia and South Africa, but throughout the globe, 
and of which the larva of the European Cwethocamba 
processionea presents a familiar example. Duncan (Nat. 
Libr. Ent. vol. vii. Exotic Moths, pp. 181-2. pl. xxii. f. 5) 
represents the larva of D. vu/#erans as possessing four 
fascicles of rufous spines, exsertile at will on both the an- 
terior and posterior portions of the body, and quotes Lewin 
to the effect that the wound inflicted by the fascicles is 
very painful. According to Mr. Murray’s account it 
would appear that the African larvae, from the handling of 
which Dr. Welwitsch experienced such suffering, were near 
allies (if not actually species of Doratzfera) ; and the con- 
clusion is obvious that it was by fascicles of spines that the 
pain was occasioned—not an uncommon case in the 
warmer parts of the world, and one by no means indi- 
cative of any special relation between the Lepidopterous 
faunas of South Africa and Australia.” 
Mr. Trimen is obviously right as to the absence of 
analogy between the venomous properties of the cater- 
pillars spoken of by Livingstone and Baynes, and those 
met with by Dr. Welwitsch, and it was a slip on my part 
to collocate them together ; but I am not satisfied that he 
is equally right in referring the pain caused by the species 
of Doratophora to mechanical irritation. He gives no 
facts in support of his assumption to that effect, and 
the facts communicated to me by Dr. Welwitsch regard- 
ing the insect from which he suffered seem to me wholly 
‘inconsistent with that supposition. It may be supposed 
from his and my silence that we acquiesed in Mr. 
Trimen’s views. But it isnotso. When Mr, Trimen’s 
paper appeared Dr. Welwitsch spoke to me upon the 
point, and I urged him to communicate to.the scientific 
world fuller details of the incident than I had given, and 
I understood that he intended to do so in any account of 
the insects collected by him. I therefore did not feel 
warranted in speaking, which I now regret, for as with 
much else that he had on hand to do, his life has been 
too short for him to do it himself. Now that he has 
passed away from us I should not like an erroneous im- 
pression to exist as to the facts; and although I have 
little to add to what | formerly stated as communicated by 
him to me, I should wish to repeat it more precisely, and 
to say that Dr. Welwitsch himself was firmly convinced 
that it was not a case of mechanical irritation but of a 
special virus of unusual potency. 
In the first place, then, Dr. Welwitsch had heard of 
this noxious caterpillar before he met with it—the natives 
knew it well and dreaded it. In the next place when he 
did meet with it his native attendant warned him of it— 
and they took every precaution against touching it ; they 
plucked leaves on which the caterpillars were feeding and 
guided them from the leaf into the wide-mouthed bottle 
or vessel he had to carry such specimens home in. They 
also took specimens of the plant on which they were feed- 
ing. I suggested to him that the sting might have been 
in the plant, but this he was positive was not the case. 
Tae virulence of the venom was such that by the time 
they reached home in an hour or so after, every tender 
NATURE 
6 
Sepa”) *% 
part of their body which they had touched with their 
fingers had become swollen and inflamed; their eyes 
were closed up, their lips and cheeks swollen as if they 
had been assisting (as principals) at a prize fight, and the ” 
consequent fever was so great that they were laid up, 
unable to move for two or three days ; and when they did 
get up he found that their attendant$ had bundled out of 
the house both the caterpillars and the plants on which | 
they fed. Now it seems to me that mechanical irritation 
is a wholly inadequate cause for such extreme inflamma- 
tory action. Mechanical irritation may go a certain 
length, but there are bounds beyond which we must look 
for some other explanation. 
But first we want more facts and more examples. I 
exhibit two caterpillars, apparently different species, which 
I have received from Old Calabar, given to me with a 
notandum as reckoned injurious if not venomous, but my 
information as to them is too vague to allow me to cite 
them as positive examples of venomous caterpillars. And 
I also show one from Brazil which I have received from 
my friend, Mr. Fry, which he informs me bears a very 
bad character in Brazil. Both of these, indeed, all to 
which this property has been ascribed, are hairy cater- 
pillars ; but then it is only hairy caterpillars that seem to 
have the necessary apparatus for stinging—all stinging 
plants, so far as I know, are hairy. If the caterpillars 
have a special venom, then, as in the nettle, there should 
be a gland at the base of each hair, which should be 
hollow, and the spines in most, if not all, our caterpillars 
are hollow. I know of no physiological reason against their 
being so made. In the skin of the newt there are pores 
which exude an acrid irritating fluid. If a hollow hair 
were placed over the pore with proper muscles, we should ~ 
then have a parallel to the supposed case. 
But, as I said before, we want information as to the 
existence and amount of this venomous property, and the 
chief object of this paper to-night is, after eliciting the 
views of the meeting, to suggest to those who may have 
the opportunity, the desirableness of making observations 
on the point. A. MURRAY 
ON SPACE OF FOUR DIMENSIONS 
WV TE 
measures the extension of the Universe. We may 
determine the form and position of any material object 
by assuming three infinite planes, fixed in infinite space, 
and at right angles to each other. Space then is the 
room occupied by matter, or included between distant 
masses of matter; and, as such, we know of it only as 
possessing three dimensions :—length, breadth, thick- 
ness. 
Descartes (Principia pars. 2, “ Quid sit spatium, sive 
locus internus”) remarks, “ For, in truth, the same exten- 
sion in length, breadth, and depth, which constitutes 
space, constituted body; and the difference between them 
consists only in this: that in body we consider extension 
as particular, and conceive it to change with the body ; 
whereas in space we attribute to extension a generic unity 
(genericam unitatem), thus after taking from a certain 
space the body which occupied it, we do not suppose that 
we have at the same time removed the extension of the 
space, because it appears to us that the same extension 
remains there so long as it is of the same magnitude and 
figure, and preserves the same situation in respect to cer- 
tain bodies around it, by means of which we determine 
the space.” 
Gauss used.to say that one of the happinesses of his 
future life would be the amplification of his conceptions 
of space; the realisation of that which he had once 
known as space of three dimensions, as space of four 
dimensions. 
infinitely attenuated book-worms in an infinitely thin 
*% 
| [May 1, 1873 Bi 
may define sface as that which indicates and 
For just as we can conceive of beings “like — 
> 
¥ 
