COXAL GLAND OF LIMULUS AND OF AEACHNIDA. 515 
tween the gland and the ventral blood-sinus. It is 
then closed by a connective-tissue trabecula, and the tube soon 
disappears from the sections. The gland epithelium does not 
end suddenly, but gradually passes into the typical connective- 
tissue cells, the extent to which it passes out into the spaces 
varying in different sections (figs. 6, 7, 8). The basement 
membrane becomes continuous with the trabeculse of the con- 
nective tissue, and on these connective-tissue cells or rather 
nuclei are scattered irregularly. 
Note on the Foregoing. 
By Professor E. Bay Laxkister. 
From the preceding observations it is clear that the coxal 
gland of Limulus has the essential anatomical features of a 
“ nephridium,” such as that of the Chaetopod worms and of 
Peripatus, viz. it is, in the young animal, a tube opening to 
the exterior by one extremity and to the primitive body cavity 
or coelom (the space between the trabeculae of the connective 
tissue) by the other ; further, it is a paired organ, occurring on 
the right and left sides of the body, and moreover the pair 
appear to belong to a single segment, and to be therefore 
possibly the single surviving pair of a number of such nephridia, 
of which one pair were developed originally in each segment of 
the body. 
The conversion in Limulus of what is in the young an ex- 
ternally-opening tubular gland into a “ ductless gland ” in the 
adult, finds a close parallel in the history of the supra-renal 
body of Vertebrata as determined by Mr. Weldon (this 
Journal, January, 1885). The coxal gland of Limulus, with 
its curious brick-red pigment, is probably not only morpho- 
logically similar to the modified bit of mesonephros which 
forms the supra-renal body of Vertebrates, but also physio- 
logically resembles that organ. 
