256 WILLIAM BLAXLAND BENHAM. 
These corpuscles can readily be seen by killing a piece of 
tissue, such as a septum or a nephridium, with 51, per cent. 
osmic, and then staining in picrocarmine. 
The Nephridia.—These have been figured by Gegenbauer 
(10) and described histologically by Claparéde (11) for Lum- 
bricus. Each nephridium or “segmental organ” of Dr. 
Williams (47) is a more or less coiled tubule with an internal 
funnel-shaped opening at one end, and an external pore at 
the other. The tube itself is divisible into three regions, 
the innermost leading from the funnel is cilated internally ; 
this leads to a glandular region, and this to a short, muscular, 
slightly enlarged “ vesicular” region. The lumen of the first 
two regions is intracellular, whilst that of the vesicle is inter- 
cellular and surrounded by muscle-fibres. The histology of 
the nephridia has not been minutely studied in any form, 
except in Lumbricus. 
Nephridia are at present known in nearly all the forms 
whose internal anatomy has been described. . 
In Digaster Perrier appears not to have detected the organ 
or its pore. Beddard did not find them in Pleurocheta. 
In most of the Perichztas they are so small as to have 
led to the impression that they are absent, but in P. robusta 
and P. affinis delicate tubules are attached to the septa, but 
Perrier gives no details. [In a Pericheta from the Phil- 
ippines I have found numerous small nephridia in each 
somite by means of sections. Beddard informs me that he 
has made a similar observation. ] 
In the worms which possess nephridia the internal funnel 
is usually situated in the somite anterior to that in which the 
tubule lies, but in Plutellus the whole organ lies in one 
somite, and it has a large vesicular portion. 
In Typheus the nephridia have only been observed in the 
anterior somites. 
In Titanus the nephridia do not commence till somite xiv. 
In Anteus those of the clitellar region are shorter, wider, 
and less coiled than the others, and are supposed by Perrier 
to function as sperm ducts. 
