of the Malpighian Tubules in the Arthropoda. 291 
*€ coxal glands ” and “ green glands” are modified nephridia. 
Sedgwick remarks (loc. cit. p. 119) that with the exception 
of these structures there are no nephridia in Arthropods 
recognizable as such; and this conclusion probably represents 
the opinion of most comparative anatomists. ‘The claim of 
the Malpighian tubules to be looked upon as nephridia has 
been more and more ignored. Gegenbaur (Comp. Anat., 
Engl. transl. by Bell, p. 276) carefully abstains from discus- 
sing the morphology of these organs. Lankester (‘ Notes on 
Embryology and Classification,’ 1877, p. 33) remarks that 
“in tracheate Arthropods the Malpighian filaments possibly 
are the nephridia.” Balfour (Comp. Embr. vol. 1. p. 568) 
doubtfully compares them to the anal vesicles of the Ge- 
phyrea. Now these structures are so widely spread among 
the Tracheata (even if the tubes of the Amphipoda are not 
of the same nature) that they must be regarded as among 
the most characteristic organs of that group. The fact that 
they do not occur in Peripatus might perhaps be regarded as 
evidence that the Malpighian tubes have arisen within the 
group; but, on the other hand, their absence from Pertpatus 
may be reasonably accounted for by the persistence of un- 
modified nephridia performing the same function: in any 
case a similar argument must be applied to account for the 
great reduction in the nephridia of the Crustacea; they are 
nephridia, and they are reduced in number, in accordance 
with the reduction of the ccelom. 
If, then, the absence of the Malpighian tubules in the most 
primitive known Arthropod, Peripatus, is not necessarily a 
real break of continuity, the segmented worms are naturally 
the animals in which one might expect to find the beginning 
of these organs, especially in the more primitive segmented 
worms, for the Gephyreans must be regarded as greatly modi- 
fied Annelids. 
In a species of Acanthodrilus, which I refer, at present 
with some little doubt, to Acanthodrilus multiporus (Beddard, 
“On the Specific Characters and Structure of certain New- 
Zealand Earthworms,” Proc. Zool. Soc. 1885, p. 813), the 
last segments of the body are almost entirely filled with 
nephridial tufts, which, as I have elsewhere stated, open by 
numerous pores on to the surface of the body and by nume- 
rous ciliated funnels into the celom. ‘The gut in this region 
of the body has a very narrow lumen and is lined by tall 
columnar cells, which are noé ciliated, as in the intestine 
generally, but covered with a delicate chitinous cuticle. 
This region of the gut is probably proctodeum. At irregular 
intervals minute cecal diverticula arise from the BOY these 
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