COXAL GLAND OP LIMULUS AND OP ARAOHNIDA. 513 
anterior end of the gland passes in front of the main mass of 
the entosternite, and is in relation to its anterior cornua. 
The blood supply of the gland could not be ascertained with 
certainty from the fact that all the specimens had been cut 
into to ensure their preservation, but from the presence of 
blood-corpuscles we can assert that some of the spaces in the 
connective tissue surrounding the gland are blood spaces, 
though there is no trace of the central blood-vessel which is 
present in the adult. 
Communication with the exterior is effected by means of the 
primary tube, which, lying ventrally and nearest to the ento- 
sternite, curves gradually away from the rest of the gland, and 
at the level of the anterior edge of the fifth appendage is 
separated from it by a muscle, passes slightly downwards, 
turns gradually, ascends close to the main artery of the limb, 
passes away from this and runs for a short distance close 
beneath the integument, and opens at the bottom of a slit-like 
depression at the base of the coxa of the fifth limb on the side 
next the fourth appendage and on the dorsal surface. At the 
base of this appendage, and of the second, third, and fourth 
limbs as well, is a very curious sculpturing which is not present 
in the adult, and which can be best understood by reference to 
fig. 13. Furrows running in various directions separate that 
part of the coxa which lies nearest to the dorsal surface of the 
animal into three lobes, which, if looked at from the dorsal 
surface, lie one distal and median, and two proximal, right and 
left ; the two proximal ones being together about double the 
breadth of the distal one. From the apex of the median lobe 
another furrow passes obliquely upwards and forwards towards 
the distal end of the limb, and soon bifurcates, giving rise to 
two right and left lobes less strongly marked than the proximal 
ones, the one nearest the fourth appendage being much smaller 
and lying more deeply than that on the side of the sixth 
appendage. Parallel to the coxa, and on the side of it nearest 
the anterior end of the body, a chitinous ridge runs, and it is 
at the bottom of the deep furrow between this and the smaller 
of the two distal lobes that the duct of the coxal gland opens. 
