NOTE ON A NEW DEEP-SEA EC H I U ROI», PROTOIJONELLI A M1TSUKURII, 263 



oogonium of various growth-phases has at its free end a cap of a compact 

 nutritive cell-mass, appearing, as in Bonellia, as a small cone with blunt 

 apex. Fully grown oogonia of about 0.45 mm. in diameter found in the 



coelom or in the oviduct are also accom- 

 panied with the cell mass which has be- 

 come a little reduced in size. 



Segmental organ or oviduct. — Only 

 the left oviduct is present attached close 

 to the ventral nerve-cord (fig. 2, od.). It 

 is cocoon-shaped, thin-walled, and provid- 

 ed with a short stalk. The whole struc- 

 ture measures about 3.5 mm. long and 

 about 1.3 mm. thick. It seems however 

 to have been a more spacious sac in the 

 living state. The internal aperture of 

 the organ is of a similar shape and posi- 

 tion as is known in Bonellia ; it is a wide 

 and notably fimbriated funnel attached 

 to the distal end of a slender tube. The 

 latter opens into the sac near the stalk or duct of the organ. The sac is 

 filled with full grown spherical eggs of about 0.45 mm. in diameter. 



Systematic position. — From the foregoing description, it will be seen 

 that this species bears, so far as the internal anatomy is concerned, close 

 affinity to the Echiuroids belonging to the genus Bonellia. It agrees very 

 closely in almost all essential characters with the female form of Bonellia, 

 viz., with respect to the ventral hooks, the alimentary canal, the anal 

 glands, the vascular system, the single oviduct, and ovarian eggs. The 

 only point of difference from Bonellia is in the shape of the proboscis. 

 But it must here be noticed that the proboscis of the Echiuroids in general 

 is a structure which varies more or less even in one and the same genus. 

 Echinrus unicinctus for instance, is almost proboscisless as compared with 

 other Echinrus species ; just the reverse is the case with Thalassema tacni- 

 oides, in which the organ can be extended to a length three or more times 



