2 BECK, ON ILLUSIVE APPEARANCES. 
came out just above the orbital bone (see Pl. I, fig. 1). On 
making a vertical section of the skull, andexamining with 
great care the vestibular sacs, I became convinced that the 
tubular ducts had no connection with them nor with the 
auditory nerve (fig. 4). Each of these tubes, which in the 
common eel is just wide enough to admit a fine piece of silk- 
gut, terminates in a membranous fold or hollow in the subcu- 
taneous tissue just above the eye (fig. 5), and contains a certain 
quantity of thin fluid or lymph, which, by the way, bears no 
resemblance to mucus. Are these cavities reservoirs for the 
supply of fluid to lubricate the surface, and may we conjecture 
that the lymph is drawn up the tubular ducts by capillary 
attraction? There is little reason to doubt that the cranial 
ducts are connected with the so-called ‘mucus system” 
which is very complicated in the eel tribe, but in what 
manner they are so I have hitherto been unable to satisfy 
myself, and leave the determination of the question to the 
investigation of more experienced anatomists. 
On the Ixttusive Appnarances produced by some TRaAns- 
PARENT Oxssects. By Ricuarp Beck. 
To view an object by passing light through it, or, as it is 
commonly termed, to look at it as transparent, 1s a method 
of examination not only peculiar to the microscope, but also 
one to which the naked eye is quite unaccustomed. It fre- 
quently conveys to the mind most imperfect ideas of an 
object, and in very many instances it produces appearances 
which even in shape bear no resemblance to the true 
structure: of this fact, which is somewhat difficult of proof, 
most conclusive evidence may be furnished by a careful 
examination of the scales of Lepisma Saccharina. 
This insect may be found in most houses, frequenting 
damp warm cupboards, or as an associate in the dark of 
black-beetles and cockroaches, and its scales have been long 
known to microscopists. 
The insect, which is very active, should be caught without 
injury in a clean pill-box with a few pin-holes in the lid, and 
a drop of chloroform over these holes will soon make the 
inmate insensible, when it may be turned out upon a piece of 
clean paper. 
