516 
G. L. GULLAND. 
The observations here recorded on the structure and connec- 
tions of the immature coxal gland tend to render it probable 
that the green glands of Crustacea (antennary coxal gland) are 
also to be regarded as a pair of modified nephridia. In figs. 14, 
15 are reproduced Grobben's drawings of the antennary glands 
of two forms of Crustacea. It seems not improbable that the 
so-called “ end-sac ” of these glands is not part of the nephri- 
dium, but is developed from the connective-tissue space 
(coelom ic space) into which the true tubular nephridium 
originally opened. It certainly would be possible to bring 
about such a structure by allowing the space into which the 
inner end of the young coxal gland of Limulus opens to 
enlarge and become vesicular instead of allowing the nephridial 
tube to close up. 
It is important to note further the possibility that other 
structures present in Arthropoda are to be regarded as modified 
nephridia. 
The demonstration of the extensive changes which the coxal 
gland of Limulus undergoes in its development opens our eyes 
to the probability of such changes in other cases. It is a 
remarkable fact (as has been pointed out by Mr. Kingsley, 
who has independently demonstrated the tubular character and 
external opening of the coxal gland in the embryonic Limulus) 
that the “ shell-gland ” of Entomostraca opens at the base of 
the fifth pair of appendages (the second pair of maxillae) in 
those animals, and thus corresponds with the coxal gland of 
Limulus and of the Arachnida in position. But when once 
the notion is admitted that ducts opening at the base of limbs 
in the Arthropoda are possibly, and even probably, modified 
nephridia, we immediately conceive the hypothesis that the 
genital ducts of the Arthropoda are modified nephridia. 
It will require careful embryological work to test this 
hypothesis. It is supported by the analogy of Vertebrata, 
where as close a connection and as direct a continuity of the 
gonad with the adventitious duct derived from the renal excre- 
tory system is attained in the male sex, as is observed in both 
male and female among Arthropods. 
