No. 416.] THE TEXAN KÆNENIA. 627 
relaxed, allowing the sac to flatten dorso-ventrally and wrinkle, 
do we obtain diminutive trachez or simple lung books. After 
examining a great number of sections one cannot refrain from 
believing that simple sac trachez like those of Koenenia may 
have given rise to both lung books and trachez in other arach- 
nids. If this be the case, we may hold that Koenenia, which 
possesses the simplest phase of these organs, the lung trachez 
(which are in reality abdominal appendages belonging to distinct 
body segments), is the most primitive of all Arachnoidea. 
Circulatory System. — As to the circulatory system, the 
simplest condition possible exists. A definite heart has not 
yet made its appearance. The blood can have no regular 
course through the lacunae and sinuses, and it probably makes 
its exchange of gases in the neighborhood of the lung sacs. 
There must be some definite region for the interchange of 
oxygen and carbon dioxide, for though Koenenia is small, its 
exoskeleton is rather too thick to allow of a general surface 
respiration. I do not think that the dots over the entire sur- 
face of the chitin can be minute pores, which the spiders alone 
of all the arachnids possess, over the skin of the abdomen. 
Reproductive System. — In the female the unpaired ovary 
begins as a blind tube in the seventh or eighth segment and 
extends into the third. From each side near the anterior end 
it is prolonged into two oviducts, consisting, for the greater 
part of their length, of large glandular cells — the largest cells, 
in fact, of the body. These ducts run forward and upward, 
becoming very small and thin-walled ; probably the last por- 
tion, for a short distance, being chitin-lined, as in Galeodes. 
In the second abdominal segment they become very much 
swollen, forming a sort of pouch on each side, filled with a 
gelatinous secretion, evidently derived from the gland cells 
of the oviduct. The duct continuing from each pouch or 
vesicle runs backward and downward to meet at the place of 
entrance in the vagina. It is this portion of the reproductive 
organ, the vitelline vesicles and their terminal ducts, of which 
Hansen and Sorensen write: “In the second abdominal seg- 
ment there is an organ which shows the same peculiar luster 
and refraction of light which one of us knows so well for the 
