426 WILSON. [VoL. III. 
these observations I cannot deny the possibility that the glan- 
dular part may be differentiated from the somatic mesoblast at 
a very early period, fusing immediately with the cells of the 
nephric cord, which may give rise only to the end-vesicle. Until, 
however, the relations of the nephridia to the nephric cords 
(which have escaped the attention of all other observers of the 
Oligochzta) have been made clear in other forms, the question 
must remain open, for I do not believe it is possible to attain 
an absolutely certain result by the study of Lusbricus alone. 
Whatever be the result, there can be no doubt in the case 
of Lumbricus of the intimate connection of the nephridia with 
ectoblastic nephric cell-cords and their partial derivation from 
them. The comparison of the nephric cord with the vertebrate 
segmental duct, which I drew in my earlier paper, has been 
criticised by Eisig, in an appendix to his monograph of the 
Capitellidz, on several grounds. I may, however, point out 
that it differs but slightly from his own views, according to 
which the vertebrate segmental duct is to be regarded as the 
posterior extension of the ectoblastic part of an anterior nephrid- 
ium, and that: it gives a datum hitherto lacking to the com- 
parison, by showing in the annelids a continuous differentiated 
ectoblastic structure connecting the anterior nephridia with 
those lying behind. As to Eisig’s criticism of my comparison 
of the nephridia of annelids with the pronephros of Vertebrates, 
I fully acknowledge its force. 
The nephridia rapidly elongate, and, owing to the fact that 
their ends are fixed, bend into a U-shape with the loop directed 
dorsally and laterally. Meanwhile the central cord of cells 
becomes perforated from end to end by a delicate canal which 
becomes ciliated ; the funnel-cell divides into a group of ciliated 
cells situated on the anterior face of the dissepiment which 
form the funnel, and the organ becomes fully functional long 
before the young worm is hatched. I have not attempted to 
follow in detail the histological differentiation. 
The Sete.— The setigerous glands of the inner or ventral 
series arise opposite the nephric cord in regular alternation with 
the nephridia, and transverse and longitudinal sections clearly 
demonstrate the fact that they take their origin in the nephric 
cords. In Fig. 86 the outer end of the nephric rudiment 
appears to turn upwards and backwards so as to adjoin the fun- 
