STRUCTURE OF UROCH^TA AND DICHOGASTER. 
241 
nephridia of Earthworms are richly supplied with blood-capil- 
laries, it seems nearly certain (particularly from the investiga- 
tions of Kiihenthal) (20) that a good deal of the waste matter 
that is excreted by them is not extracted from the blood- 
capillaries by the cells of the nephridia, but is taken up by 
the funnels ; the large granular peritoneal cells which clothe 
the intestinal blood-vessels play an important part in this 
process of elimination. 
Now, the very differences between the mucous gland and the 
other nephridia suggest that it plays a different part in the 
economy of the animal. A suspicion that this was the case 
led M. Perrier to term it “ glande h mucosite,” although he 
had no evidence to bring forward of a positive nature ; this 
supposition would account for the reduction of the ciliated 
funnels ; the high development of the secreting part of the 
organ, and the presence of a large vesicle for the storage of the 
secretion, coupled with the reduction of the ccelomic apertures, 
is clearly in favour of the view that this gland secretes a sub- 
stance which is used for some definite purpose. 
I describe below (p. 258) the structure and relations of the 
anterior section of the nephridial system in Dichogaster. 
This worm has an anteriorly situated gland which resembles 
in many particulars the mucous gland of Urochaeta. It 
consists of a tuft of highly convoluted tubules which have the 
same structure as nephridia ; these tubules open by means of a 
wider duct; the segments (Nos. 1 — 3) occupied by this gland 
contain no other nephridia. The “mucous gland” of 
Dichogaster differs from that of Urochaeta in cer- 
tain important particulars; in the first place it has 
no coelomic funnels; in the second place the duct 
opens, not on to the exterior of the body, as in 
Urochaeta, but into the buccal cavity; thirdly, it 
appears to be formed by a single tube much coiled. 
Apart from these points of difference, the similarity between 
the two glands is so great that I cannot but regard them as 
homologous. The fact that the mucous gland of Dichogaster 
opens into the buccal cavity suggests that its function is 
