On an Australinn Land Nemertine. 95 



of the wall of the proboscis slieath consists of longitudinally 

 and circulai-]y disposed fibies irregularly mixed together, 

 and not arranged in definite layers as seems to be the case 

 in otlier Hoplonemertines* Just in front of the anterior 

 attacliment of the proboscis, and just behind the mouth, the 

 wall of the rhynchod?eum-f- forms a kind of muscular sphincter, 

 which, when the proboscis is con)pletely withdrawn, closes 

 the entrance. This is not seen in any of the sections figured, 

 but it is ver^^ distinctly visible in horizontal sections of a 

 specimen killed with the proboscis retracted. 



The cavity of the proboscis sheath, or rhynchocoelom, is 

 filled with a liquid in which float numerous elongatedly 

 spindle-shape<l corpuscles, each about 009 mm. in length 

 and about 00030 ram. in greatest transverse diameter. The 

 two ends of the spindle are very gradually and shar))ly 

 pointed; the substance of which it is composed stains fairly 

 well with hiematoxylin, and is scarcely at all granular except 

 in the middle of the cell, where there seems to me to be a 

 nucleus. Von Graff describes similar but smaller bodies in 

 Geonemertes chalicophoiu, but states that they have no 

 nucleus. I can offer no suggestion as to the possible use of 

 these remarkable bodies. 



On slitting open the proboscis sheath in an animal which 

 has been killed with the proboscis retracted the latter organ 

 is seen packed aw; y in the sheath in a much bent and 

 crnmpled condition. 'J'he folding of the proboscis witldn 

 the sheath appears to be very irregular, and is neces.sitated 

 by its great length, which far exceeds that of the sheath 

 which has to contain it. If we now gently pull the 

 proboscis away from the sheath (Fig. 13) we shall find that 

 it is attached to tlie latter at two points, (1) at the anterior 

 extremity, where the muscular walls of the sheath and 

 proboscis become continuous all lound (Fig. 6, "in. p., Fig. 13, 

 rt. rt., Figs. 12 and 14, a.'tt'), and (2) at the posterior 

 extremity of the proboscis, which narrows out to form a 

 long retractor muscle (Figs. 13, 14, r. m) whose end is 

 attached to the inner surface of the wall of the sheath 

 a little in front of the blind end of the latter (Fig. 13, ^?. «.) 



The proboscis consists of three main divisions — (1) most 

 anterio]-ly, the eversible portion (Figs. 14, 15, e. r) which is 



* Vide vou Graff, loc. cit. 



t The rhyuchodaBum is the cavity into which the proboscis sheath and 

 alimeutary canal both open. 



