388 Pub. Ftiget Sound Biol. Sta. Vol. 2, Xo. 55 



pied by each experiment and in order that this temperature might be the 

 same as that in which the animals normally live. The temperature varia- 

 tion during such an experiment was generally about one degree Centigrade, 

 sometimes more, sometimes less, but never more than two degrees. The 

 temperatures recorded during the summer of 1920 varied from 10.5 to 

 13° C. 



2. Experiments on sea-urchins. Small individuals of Strongylocen- 

 trotuft drobachiensis and S. frnnciscanus were used, usually one individual 

 being placed in each experimental bottle. The results are tabulated in 

 table 1. Experiment 1 was performed on S. frnnciscanus; the other ex- 

 periments on S. drobachiensis. 



3. Experiments on starfish. Small individuals of Asterias victoriana 

 were employed, one in each bottle. The results are given in table 1. 



4. Experiments on sea-cucumbers. These experiments were per- 

 formed on small individuals of Cucumaria chronhjelmi (Nos. 1 to 3), 

 Stichopus californicus (Nos. 4 to 6) and Cucumaria japonica (No. 7.) 

 The results are tabulated in table 2. 



5. Experiments on chitons. The species used was Catherina tunicata. 

 The data are given in table 3. 



6. Experiments on bivalves. Mytilus edulis was employed, gen- 

 erally two individuals in each bottle. The animals were placed in the 

 experimental bottles the day before the tests were carried out in order 

 that they might fasten themselvs to the glass. The results are given in 

 table 3. 



7. Experiments on nudibranchs. Three species of nudibranchs were 

 used, of which only one was identified. The species identified was 

 Triopha carpenteri, employed in experiment 1, table 4. The form used 

 in experiment 2 was a large white Dorid, probably an Anisodoris. The 

 third species, used in experiments 3 to 5, was the little brightly colored 

 Eolid, very common on the eel grass at Friday Harbor. As this species 

 is rather small, five or six individuals were placed in each experimental 

 bottle. The data on the nudibranchs appear in table 4, 



8. Experiments on crabs. The common purple shore crab, Hemi- 

 grapsus nudus, was used. Two or three individuals were placed in each 

 experimental bottle. This species was found to be remarkably susceptible 

 to cyanide. The results are given in table 5. 



