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PROFESSOR E. RAY LANKESTER. 
up-standing appendages. They are from the first introverted, 
and remain so. It also agrees with the disposition of the cuti- 
cularised surfaces of the Scorpion’s lung-book, as seen in the 
adult. The cuticularised surface remains in the in-pushed as 
it is in the out-growing appendage, the surface in contact with 
the air. Each bag-like lamella is introverted together with the 
axis of the limb ; and one cannot better picture to oneself the 
relative conditions of out-growth and in-growth than by fixing 
a kid glove by the margin of its opening to the margin of an 
opening of the same size on the outside of a box. The coloured 
surface of the kid will represent the cuticle, the fingers the 
lamellae, the hand the axis. Thus tbe glove will represent a 
lamelligerous appendage, standing up on the ventral surface of 
an Arthropod, its cavity communicating with the cavity of the 
venous sinus of the animal, as the cavity of the glove does with 
that of the box. 
Now, without removing the glove, push all the fingers from 
their tips inwards into the hand, and then the hand into the 
box, so as completely to turn the glove outside in. Thus the 
glove will represent the appendage when introverted into the 
veinous sinus as in the modern Scorpions. 
The tips of some of the introverted lamellae of the Scorpion’s 
gill-book have aquired laterally, but not in every part, an 
attachment to the wall of the veinous sac into which, they have 
pushed their way. These attachments and the relation of 
blood-space, air-space, and cuticle in the lung-lamellae of 
Scorpio are figured in the 'Trans. Zool. Soc.,’ vol. xl, 1885. 
