4 AKT. 11. A. IZUKA : OBSERVATIONS OX THE 



of Professor K. Osawa, whose interest in the study of the worm 

 I have already had occasion to mention. 



The characters of the species may be summarily stated as 

 follows : 



Immature worm (PL I., fig. 1). — Number of segments as 

 many as 300. Praestomium subhexagonal with broad base ; 

 anteriorly concave on the sides ; provided with a pair each of 

 tentacula and subtentacula, and a pair of eyes. Peristomium 

 with four pair« of tentacular cirri. Proboscis protrusible, with 

 soft papillae and a pair of jaws. Parapodia nearly similar through- 

 out the body, being biramns ; only the lower ligula of the dorsal 

 ramus is present. Both the dorsal and the ventral cirri are 

 simple. Pygidium with a pair of slender anal cirri. 



Mature worm (PI. I., figs. 6, A, B). — This is the head-bearing 

 anterior portion of the original worm. The segments number 7<S 

 or less. They are distinguishable into those of the 1 Ik »rax and 

 of the abdomen. Head and thoracic segments remain unchanged 

 in character, except that the eyes are now more conspicuous 

 than before. Abdominal segments enlarged ; their bristles, ori- 

 ginally of the ordinary form, are now replaced by paddle-shaped 

 ones. 



Geratocephale osawai is one of the most common littoral 

 Annelids in Tokyo and vicinity, where it is extensively used in 

 both immature and mature phases as bait. The immature phase 

 is locally known under the name of " Itome " and the mature 

 phase under that of " Bachi." 



The species is also known to me from Miya in the Province 



