ZOOPHYTES. 397 



which they spring ; with a head -like lobe at the summit, 

 separated from the body by a constriction, immedi- 

 ately below which two lengthened arms project in a 

 direction towards the axis of the tube. 



Such is the external form of these animals, and 

 their movements are still more extraordinary. The 

 head-lobe of each one moves to and fro freely on the 

 neck, the body sways from side to side, but still more 

 vigorously backward and forward, frequently bending 

 into an arch in either direction ; while the long arms 

 are widely expanded, tossed wildly upward, and then 

 waved downward, as if to mimic the actions of the 

 most tumultuous human passion. 



Whenever the Sabella protrudes from its tube, these 

 guardian forms are pushed out, and remain nearly in 

 contact with the Annelid's body, moving but slightly ; 

 but no sooner does it retire than they begin instantly 

 to bow forward and gesticulate as before. These move- 

 ments are continued, so far as I have observed, all the 

 time that the Sabella is retracted, and are not in any 

 degree dependent on currents in the surrounding water, 

 whether those currents be produced by the action of 

 the Annelid or by other causes. They are not rhyth- 

 mical ; each individual appears to be animated by a 

 distinct volition. 



Applying a higher magnifying power than we have 

 yet used to the animals, we find that the head-lobe en- 

 closes a central cavity ; that the arms are also hollow, 

 with thick walls, marked with transverse lines, indicat- 

 ing flattened cells, and muricated on the exterior; and 

 that the body contains an undefined, sub-opaque nucleus, 

 doubtless a stomachal cavity. 



I cut out, with fine scissors, a segment of the tube, 



