gastric caeca.

1 to 6, The bases of the six prosomatic limbs.
A, prosomatic gastric gland (sometimes called salivary).
B, Coxal gland.
C, Diaphragm of Newport = fibrous flap of the entosternum.
D, Mesosomatic gastric caeca (so-called liver).
E, Alimentary canal.

(From Lankester, _Q. J. Mic. Sci._, vol. xxiv. N.S. p. 152.)]

7. _Ovaries and Spermaries: Gonocoels and Gonoducts._--The scorpion is
remarkable for having the specialized portion of coelom from the walls
of which egg-cells or sperm-cells are developed according to sex, in
the form of a simple but extensive network. It is not a pair of simple
tubes, nor of dendriform tubes, but a closed network. The same fact is
true of Limulus, as was shown by Owen (7) in regard to the ovary, and
by Benham (14) in regard to the testis. This is a very definite and
remarkable agreement, since such a reticular gonocoel is not found in
Crustacea (except in the male Apus). Moreover, there is a significant
agreement in the character of the spermatozoa of Limulus and Scorpio.
The Crustacea are--with the exception of the Cirrhipedia--remarkable
for having stiff, motionless spermatozoids. In Limulus Lankester found
(15) the spermatozoa to possess active flagelliform "tails," and to
resemble very closely those of Scorpio which, as are those of most
terrestrial Arthropoda, are actively motile. This is a microscopic
point of agreement, but is none the less significant.

In regard to the important structures concerned with the fertilization
of the egg, Limulus and Scorpio differ entirely from one another. The
eggs of Limulus are fertilized in the sea after they have been laid.
Scorpio, being a terrestrial animal, fertilizes by copulation. The
male possesses elaborate copulatory structures of a chitinous nature,
and the eggs are fertilized in the female without even quitting the
place where they are formed on the wall of the reticular gonocoel. The
female scorpion is viviparous, and the young are produced in a highly
developed condition as fully formed scorpions.

[Illustration: FIG. 28.--The right coxal gland of _Limulus
polyphemus_, Latr.

a^2 to a^5, Posterior borders of the chitinous bases of the coxae of
the second, third, fourth and fifth prosomatic limbs.
b, Longitudinal lobe or stolon of the coxal gland.
c, Its four transverse lobes or outgrowths corresponding to the four