i88o.] 
Correspondence . 
279 
DEVELOPMENT AND DIFFERENTIATION. 
To the Editor of the Journal of Science. 
Sir, — We generally find that the processes of development and 
differentiation go hand in hand, the former being scarcely con- 
ceivable without the latter. Thus animal species which are 
scarcely distinguishable when in the embryo state become more 
and more unlike each other as they come to maturity. But 
there are some cases which I, at least, feel unable to bring under 
this rule. Thus there are certain Lepidoptera whose caterpillars 
are not only as distinCI, respectively speaking, as the mature 
inseCts, but where the diagnosis of the latter is scarcely possible 
without reference to the caterpillar. Hence the structure of the 
larvae is more and more taken into account in determining and 
classifying inseCts. — I am, &c., 
An Entomologist, 
A DIFFICULTY TO SOLVE. 
To the Editor of the Journal of Science. 
Sir,— Turning over some old notes I came upon the following 
record of faCts, which may perhaps interest some of your 
readers : — A wealthy landowner was seized with the whim of 
converting a village upon his estate into a town. Among other 
steps to this end he ereCted at one entrance a gateway modelled 
after those of mediaeval fortified cities, with an arch over the 
road surmounted by several rooms, which I suppose were to 
represent the dwelling of the warder. It soon became noised 
abroad that whoever slept in one of these rooms, no matter what 
might be his constitution or his habits, was, in nine cases out of 
ten, attacked with nightmare of a very violent kind. I heard all 
the particulars from a scientific gentleman who had taken much 
pains to trace the cause of this singular phenomenon, and had 
passed many nights in the room, but without being able to find 
the slightest clue.— I am, &c., 
Senex. 
VOL. II. (THIRD series). 
X 
