ARENICOLA, PARASABELLA 107 



lateral body wall, and a single retractor muscle, which has 

 its origin on the midventral body wall. 



Nephridia. — Location? Number? To see them clearly, 

 cut the oblique muscles. With a hand lens, distinguish the 

 funnel with its fringed dorsal lip and its simple ventral lip. 

 The excretory tubule is divided into an excretory portion and 

 a bladder. The latter communicates with the outside through 

 the nephridiopore. 



Gonads. — Each is a minute body attached to the posterior 

 margin of the lip of the nephridial funnel. They occur on 

 the last five pairs of nephridia. The reproductive cells are 

 discharged to the outside through the nephridia. 



Nervous System. — Push aside the digestive tract and fol- 

 low the ventral nerve cord forward to the first septum. The 

 brain and circumesophageal connectives can be found more 

 easily when the proboscis has been completely retracted. 

 Remove the pins at the anterior end, pull in the proboscis 

 with a pair of forceps, and then pin the specimen down again. 

 Usually an otocyst can be found on each side attached to 

 the connective about one third of the way from brain to ven- 

 tral nerve cord. 



Ashworth: Arenicola (the Lug-worm). Liverpool Mar. Biol. Com. 



Mem., 11, 1904. 

 Gamble and Ashworth: The Anatomy and Classification of the Areni- 



colidae with Some Observations on their Post-larval Stages. Quart. 



Jour. Mic. Sci., 43, 1900. 

 Strunk: Excretions-Physiologie der Polychaten Arenicola marina und 



Stylaroides plumosus. Zool. Jahrb., Abt. Allgem. Zool. u. Physiol. 



Tiere, 47, 1930. 



PARASABELLA MICROPHTHALMA 



This worm belongs to the family Sabellidae. It builds 

 leathery, muddy tubes on piles, among tunicates, algae, etc. 



1. In addition to the general size, form, and color of the 

 worm, observe the reduced condition of the* parapodia, and 

 the arrangement and general structure of the branchiae or 

 gills. These structures are modifications of the palps and 

 not of the parapodia, as in the other species which have been 



