8. 



adult siphon, beaxs a cluster o£ filaments at its tip. 



"When retracted tlie tentacle presents a series of trans- 

 verse ivrinkles, figure 6, Beneath the layer of epithelium, 

 figure 8, ep. run strands of longitudinal muscle fibers, Im. im- 

 bedded in connective tissue. On the side of the tentacle near- 

 est the mantle lobe to which it is attached, inside the muscle 

 layer, is a large ner\re, tn, which can be easily traced to the 

 tentacle's tip. This nerve is a branch of the pallial zierve. 

 It is not given off directly opposite the base of the tentacle, 

 but some distance above it, and the two ner^res continue along, 

 side by side, until the tentacle is reached. The appearance of 

 the two ner\'-es lying side by side, is cjaite like^a ganglioxv an.d 

 has, no doubt, been mistaken for one. On the side of the ten- 

 tacle opposite the nerve, also within the muscle layer, is a more 

 or less definite blood space, bs. 



Extension of the tentacle seems to be accomplished sole- 

 ly by forcing blood into this space. In favorable cases blood 

 corpuscles can be seen moving along it wflien the tentacle is being 

 extended, -x 



^If considerable force is exerted in extendeing the ten- 

 tacle, S77el lings, figure 7, may occur in it. Such swellings are 



