17 



The amputated animals were placed in traps the sides of which 

 were made of wire-netting permitting the free circulation of water. 

 Mud and ooze from the ocean-bed were put into the traps to a depth of 

 four or more centimeters, and they were immersed in the sea and tied 

 to a wooden pier so that they could easily be drawn out of the water and 

 their contents examined. This precaution was rendered necessary after 

 it had been found that the animals usually died within a week after the 

 operation when kept in dishes under running water in the laboratory. 

 Two animals of each lot operated upon were killed for examination at 

 intervals of three days. 



Before the work with Thyone hriareus was completed, several 

 questions suggested themselves which it was thought the results of fur- 

 ther experimentation might answer. When the rich material of the Bay 

 of Naples was placed at the writers disposal it was determined to resolve 

 these questions, if possible. 



All the individuals operated upon were given the same conditions 

 after the operation; i. e. they were placed in perforated celloidin boxes 

 or in glass jars and immersed in an aquarium of running water. Nor- 

 mal individuals of each species, were also placed in boxes in the aqua- 

 rium, in order that the effect upon normal individuals of the conditions 

 under which the regenerating individuals were kept, might be observed. 



Among the Holotkiiria observed at Naples, Cucumaria gruhi was 

 found best adapted to the aims in view, because it survived conditions 

 and operations which caused the death of other species, and because 

 the podia are arranged along the radii. Therefore two-hundred and 

 thirty-nine (239) individuals were operated upon in various ways: 



Exper. no. 1. In forty-two individuals the body was divided trans- 

 versely just posterior to the lantern. Both anterior and posterior parts 

 were given an opportunity to regenerate. 



Exper. no. 2. Each of forty-two individuals was divided into three 

 parts in such a way that the anterior end contained the lantern and 

 attached organs ; the middle-piece contained the reproductive organs, 

 the greater part of the intestine, and the upper part of the respiratory 

 trees. The posterior part contained a short piece of the intestine attached 

 to the cloaca, and the lower portions of the respiratory trees. 



Exper. no. 3. Each of thirty individuals was divided transversely 

 into two equal parts. 



Exper. no. 4. Each of fifteen individuals was divided transversely 

 into two parts in such a way that the posterior part contained only the 

 cloaca, and was about one-sixth (VVi) of the body-length. 



Exper. no. 5. Each of fifteen individuals was divided transver- 

 sely into two equal parts and all organs removed. 



2 



