258 \VM. E. HITTER. 



doubtedly effected almost wholly by the contraction of the radio- 

 longitudinal muscles. The extension is probably accomplished, 

 as Spengel believes, by the inflation of the collar ccelom with 

 water through the collar funnels. 



Observation on the movements of the animal furnishes little 

 satisfaction to one's quest after a reason for the existence of the 

 peduncle that joins the proboscis and collar. At the same time, 

 however, such observation does emphasize the importance of the 

 slender isthmus's being both strongly constructed in itself and 

 also firmly anchored at the ends to the larger parts of the body 

 into which they are inserted. As the animal draws its long body 

 about by its proboscis, it frequently looks as though the slender 

 peduncle would be pulled out by the roots, particularly at its 

 collar end. One naturally conjectures that the existence of the 

 peduncle is to increase mobility at this particular place, and 

 this perhaps is its significance, though it is not clear that the 

 peduncle is in reality more flexible than the proboscis, especially 

 when the latter is perfectly flaccid, for I have seen this part when 

 the animal was in its canal double back upon itself so as to bring 

 the two limbs into contact throughout their length, the tip of 

 the organ being carried back to its base. The collar and 



o o 



thoracic portions of the body, however, are always, and the 

 proboscis when muscular contractions are in progress, relatively 

 rigid ; and it is probably under these conditions that the mobil- 

 ity assured by the peduncle, finds its importance. 



Having now the facts before us relative to the movements of 

 the animal, we may consider the anatomical structures upon 

 which these depend. 



The proboscis possesses a typical dermo-muscular tube and its 

 movements are essentially of the wave form usual to this type of 

 musculature. The close resemblance between the movements 

 of the enteropneust proboscis and those of the nemertean may be 

 especially mentioned. 



The thorax-abdomen, also, may be regarded as possessing the 

 dermo-muscular tube, though here circular muscles are either 

 altogether wanting or are very imperfectly developed, so that the 

 wave movement does not here take place. Furthermore the 

 longitudinal muscles are much stronger in the ventral than in the 



