AUTOTOMY OF HYDRANTH OF TUBULAKIA. 177 



25 C. A control was placed in the shadow near it. 1 Within 

 half an hour evidences of autotomy became apparent and within 

 one and one half hours, over half of the hydranths had been 

 lost. In the control, where the temperature of the water regis- 

 tered 5 degrees lower (25 C.), the hydranths were retained for 

 half a day. More striking still was the rapidity of autotomy 

 in the case of the fingerbowl of specimens placed in an apartment 

 immediately over the boilers of the engine-room of the Bureau of 

 Fisheries Laboratory where the temperature is constantly at 33 

 C. In this case all of the hydranths had fallen entirely from 

 the stems within two hours, while a few had fallen within one 

 hour. 



(&) Cold Effects. A fingerbowl of specimens, 12 in number, 

 was placed in an ice-chest at a temperature of 8 C. The 

 hydranths in this case were retained for three weeks and un- 

 doubtedly would have persisted had not the experiment been 

 terminated accidentally. The specimens were examined from 

 day to day and they gave every indication of being normal, 

 inasmuch as the tentacles were active at all times. Food was 

 provided for the hydroids, but it was not possible to deter- 

 mine whether they fed or not. In another set of experiments, 

 specimens were kept a week at a temperature of 10 C. in a 

 fingerbowl resting in chipped ice, the bowl being placed in 

 diffuse light. At the end of the week, the individuals were 

 apparently healthy and no indication of autotomy could be de- 

 termined. 



It cannot be urged against these experiments that the animals 

 became benumbed and their activities thereby lessened with con- 

 sequent retention of the hydranths, for as we have seen, they 

 were aparently normal and active throughout. 



2. Effect of Sunlight. In the experiments with the effects of 

 light, it was necessary to insure against heat effects. Various 

 methods were used for obviating this factor. A large vessel, 

 with a volume of about six gallons, was provided with a plat- 

 form which rested about ten centimeters from the bottom of the 

 vessel and fifteen from the surface of the water over it. On 

 this platform, a fingerbowl of Tubuloria stems was placed. Then 



1 The possibility of light being the factor here is considered later. 



