78 Journal of Entomology and Zoology 



reddish purple and the nucleus blue-black. These cells are found 

 only in the front part of the prostomium. Associated with these 

 in location are a number of mucous cells which have invaded the 

 brain and from their staining reactions seem to be functional (Figs. 

 5, 10;h). 



Cross-connective part of the brain. The main part of the brain 

 contains the fibrilar cross-connections for the whole brain. The 

 brain cells are practically all confined to the dorsal side. The eyes, 

 four in number, are buried in this cell layer. The central pair is 

 very small and vestigial, none of the lense structure remaining and 

 but little of the pigment. The lateral pair is complete, with lense 

 and cup-shaped pigment layer, but in all of the specimens I have sec- 

 tioned the eye is inverted, with the pigment outside and the lense 

 facing down toward the brain. As if to render this ocular paradox 

 more striking the perfect eyes are deeply embedded in the head and 

 the degenerate eyes are just under the cuticle. This is a rather 

 interesting example of degeneration. 



From the rear of the brain extend the circumoesophageal com- 

 missure and the nuchal ganglia. The former is biramous, divid- 

 ing on each side into a dorsal and ventral branch. This is analagous 

 to the phenomenon found in Nepthys where the ocular and surface- 

 sensory parts of the brain are separate structures. (Quatrefages; 

 44.) 



The nuchal ganglia (Figs. 13, 1, 4; W, are connected to the brain 

 by means of two nerves .3 mm. apart, .03 mm. in diameter and 

 4 mm. long. These nerves come out from the "punkt-substanz" of 

 the brain immediately below and behind the central pair of eyes, 

 follow along the nuchal pits for some distance, when they join on 

 the two nuchal ganglia on their lower front surface. The nuchal 

 pits act as a pair of narrow-mouthed sacks opening, close together 

 just under the lip of the peristomium, enlarging as they go in until 

 they are large enough to contain in their thin chitino-membranous 

 sack, each, a ganglion. The apparatus bears a rather vague resem- 

 blance to the otocyst found in Arenicola (Ehlers, '92) , but inasmuch 

 as there are no otolyths to be found and the only cavity to contain 

 them is very small and pyramidal instead of round, the diagnosis 

 is doubtful. The thing could hardly be functional, but is probably 



