626 THE AMERICAN NATURALIST. [Vor. XXXV. 
digestive tract is thus admirably constructed for such an 
illegitimate practice as egg-sucking. 
Excretory System. — I have succeeded in tracing the pair of 
tubular glands, **tappezzata d' un semplice strato di cellule epi- 
teliali," of which Grassi speaks. According to him, these 
glands extend through a large part of the cephalothorax, and 
perhaps have their orifice in front of the third pair of limbs. 
These excretory organs in reality arise in the second segment 
of the abdomen, and after forming one or two convolutions run 
into and straight through the thorax, to terminate between the 
second and third pair of appendages. There being no Mal- 
pighian tubules in the small animal, this simple pair of coxal 
glands would seem to represent the only excretory organs, 
unless, indeed, the glandular cells around the respiratory sacs 
can be considered as possessing excretory functions. If this 
be the case, the eversible sacs will then have a double func- 
tion of respiration and excretion like the vertebrate allantois. 
These cells are not represented in the drawings. 
Respiratory Organs. — Respiration in so small an animal as 
Koenenia must necessarily be very simple, and, if I have rightly 
interpreted the facts, we have in this minute Palpigrade the 
most primitive form of respiratory organs. These organs con 
sist of the three pairs of lung sacs which are situated in seg- 
ments four, five, and six, with their corresponding orifices on 
the ventral surface. They are evidently evaginated through 
the internal blood pressure. For each pair of sacs there 1$ 
a pair of dorso-ventral muscles, corresponding to the dors 
ventral muscles of Thelyphonus, which have the function in 
Keenenia of drawing in the everted sac appendages. These 
lung sacs possess on their inner surface (inner when they are 
evaginated) granular bodies which stain a deep blue with alco- 
holic carmen if they happen to be invaginated, but which take 
on a normal red stain when the sacs are thrown out. Often, 
in examining sections through the inverted sacs, one can i 
refrain from calling them tracheze, so very much do they loo 
like simple tubes. In truth, according to whether the sacs are 
pulled in by muscles, remaining contracted, or whether they 
have been pulled in by muscles that have immediately become 
