196 
towards the aperture of the nephrostome. The leneth of 
the nephridium is about ‘3 mm. The walls of its middle 
portion already contain numerous excretory granules, 
most of which are yellow, but others are almost colourless. 
The ciliary action in the tube, especially in its posterior 
part, 1s very vigorous at intervals. The first nephridium 
is more slender than any of the others and its lumen, 
especially in the anterior part, is very minute. Its 
anterior end (nephrostome) forms a slight swelling on the 
anterior face of the third diaphragm, due almost entirely 
to the larger lip, between which and the smaller lip there 
is a slit-hke opening. The larger lip bears a number of 
well-marked cilia, but no ciliated processes like those on 
the other nephridia could be seen. The relation between 
the funnels of the nephridia of these post-larval stages 
and those of the adult is unknown. Goodrich holds that 
the adult funnel is not a nephrostome but a genital funnel 
which is developed from the coelomic epithelium and is 
added to the anterior end of the nephridium. The gonads 
are not yet distinguishable. 
The brain is divisible into a large anterior part (not 
yet sub-divided into two lobes) consisting of neuropile with 
a thick covering of cells, a posterior part which is bilobed, 
each lobe having a fibrous core with a cellular covering, 
and a middle region uniting the two. The ventral nerve 
cord is more closely united with the epidermis than it is in 
the adult. No giant fibres or giant cells are recognisable. 
SystTEMATIC Postr1on AND CLASSIFICATION OF THE 
ARENICOLID.®. 
Benham” divides the Polycheta into two branches— 
the Phanerocephala and the Cryptocephala. The chief 
= 
* Polycheta in Cambridge Natural History, Worms, Rotifers 
and Polyzoa. 1896. 
