POLYCHiETA— BENHAM. 29 



Remarks. — From these suutherii seas, four species of Autolytus have been recorded — • 

 A. maclearanns Mcintosh, A. gibber Ehlers, A. simplex Ehlers; in addition to 

 Gravier's species. But the last is the only one in which tlie " ailerons " 

 are developed, as Ehlers has pointed out (1913). 



Epitokous phases. 

 A considerable number, some 3-4 dozen, of male and female epitokous stages were 

 collected on the surface at Boat Harbour. They are described by Dr. McLean as being 

 "' reddish in coloiu"." In the preserved state some are deep brown, others pale brown, 

 and others again almost white ; they all agree in their structure though it may be that 

 the darker ones are older than the rest*. 



The brown ones are of deeper tint on the ventral than on the dorsal surface, 

 which suggests that the worms swim on their backs at this time. Naturallv they vary 

 in length, the majority being from 12-18 mm. In each case I have chosen for description 

 one of the largest specimens. 



Sacconereis. 



The majority of the females have lost the ventral egg-sac, though this is still 

 present in one that was mounted, where it lies behind the 1.5th cha^tigerous segment. 



A complete large individual, measuring 38 mm. in length with a breadth of 5 mm., 

 consists of a " head "' with 14 unmodified segments, plus 40 segments with longer 

 parapods, each carrying a bundle of long capilliform notopodial bristles ; this region is 

 followed by 30 umnodified posterior segments. 



The head in this phase undergoes little modification ; there are no additional 

 prostomial appendages ; but the eyes are enlarged, specially those of the anterior pair 

 which have become thrust down to the under surface. 



The ailerons are distinct. 



The dorsal surface of the body is marked by intersegmental bands of yellowish 

 brown pigment which encroach more or less on to the surface of the segments. The 

 dorsal cirri retain the colouration of the atokous phase, brown with a white line along 

 each face. 



Polybostrichus. 



In the male, the prostonuum is white, but the appendages are more or less deeply 

 tinted. The tentacles are brown on the anterior or ventral faces, and white dorsally ; 

 the frontal tentacles, like the " bifurcated appendages," are deep browm ; the dorsal 

 cirri are paler dorsally than ventrally. 



A complete individual, measuring 32 mm. in length, consists of a " head " with 

 14 unmodified chaetigerous segments, followed by 45 segments with long capilliform 

 bristles, behind which are again some 20 unmodified segments. 



* When placed in water previous to being stained in alum-carmine the pigment is dissolved, and the water becomes 

 colonred an orange-brown, 



