380 ELIZABETH S. P. REDFIELD 



cut off, the animal can also still progress in a leech-like manner. 

 Consequently the grasping organ is not essential for this mode 

 of locomotion. Animals in a dish of water held in a current, 

 attach themselves to the substratum by the tail, but not by the 

 grasping organ, thus showing that the grasping organ is not 

 used to prevent the animal from being washed away. 



In my own experiments, however, there is nothing to show 

 that the grasping organ may not be used for locomotion; the 

 point insisted upon is the importance of its relation to feeding.' 



SUMMARY 



From the foregoing it is evident that the grasping organ of 

 Dendrocoelum lacteum is primarily employed by the animal in 

 feeding. This grasping organ is used to seize and hold material 

 on which Dendrocoelum lacteum feeds. It is stimulated to 

 activity by appropriate materials applied to the receptors located 

 on the anterior part of the worm. The grasping organ may be 

 used in certain forms of locomotion, but it is not essential to 

 this operation. 



POSTSCRIPT 



Since the completion of this paper, a note by Julius Wilhelmi, 

 Einige biologische Beobachtungen an Siisswassertricladen, has 

 been published in the Zoologischer Anzeiger, Bd. 45, pp. 475-479, 

 in which these grasping reactions are recorded. 



BIBLIOGRAPHY 



Gamble, F. W. 1896. Platyhelminthes and Mesozoa. The Cambridge Natural 



History, London, vol. 2, pp. 1-96. 

 Ijima, I. 1884. Untersuchungen liber den Bau und die Entwicklungsgeschichte 



der Susswasser-Dendrocoelen (Tricladen). Zeitschrijt jiir wissenscliaftliche 



Zoologie, Bd. 40, pp. 359-464, Taf. 20-23. 



