276 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



toAvards the aperture of the nephrostome. The length 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, is 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-like 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 ccelomic 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. 



Systematic Position and Classification or the 



Arenicolid^e. 



Benharn* divides the Polychseta into two branches — 



the Phanerocephala and the Cryptocephala. The chief 



* Polychseta in Cambridge Natural History, Worms, Rotifers 

 and Polvzoa. 1896, 



