EXPERIMENTS. 185 



III. Respiration. — Eight hours after operation. In air. As the gills behind the cut 

 began their opening phase, the left gills started first, and apparently dragged the right ones up 

 with them. When the gills closed, the left started down first and dragged the right after. The 

 operculum and the first gill behaved normally. 



When the crab was put back in water, the respiratory movements would begin as described 

 above, but after a while they would become more nearly normal. From this it would appear 

 that the coordination of respiratory movements is brought about in some part of the nervous 

 system anterior to the abdominal neuromeres. Same results were obtained on seven succes- 

 sive days, the abnormality of the respiration in air being greater than in water. 



IV. Swimming Movements. — Jul)- 23. The right and left operculum, the right and left 

 first gill and the four posterior left gills performed normal swimming movements in unison. 

 All the right gills behind the cut were either quiet, or respiring, while the others were swim- 

 ming. This indicates a center for the swimming movement of the gills in front of the free 

 abdominal neuromeres. 



Experiment X. 



July ig, 1898. Male. Both cords were cut between the neuromeres of the first and second 

 gills, H. 10. • 



I. Respiration. — a. July 29. In water. All the gills were breathing, but out of rhythm 

 The operculum and first gill moved together, but out of time with the posterior gills. In the 

 anterior group, the operculum was the first to start each inspiratory movement, and was followed 

 up by the first gill. The four gills behind the cut beat fairly well together, but the rhythm within 

 the group is imperfect and all are out of time with the anterior group. In the respiratory move- 

 ment of these four posterior gills, the most posterior one was the first to start the upward move- 

 ment. Results indicate that the gills behind the cut have been separated from their center of 

 coordination. 



b. July 23 to 28. The four gills behind the cut frequently performed the "cross rubbing" 

 or "scraping" movement, the first gill not participating. This "cross rubbing" movement of 

 the posterior gills was always followed by strong swimming movements of the operculum, first 

 gill, and thoracic appendages. At times, the operculum and first gill would stop, while the 

 appendages behind the cut kept on with unbroken rhythm; or the appendages in front of the 

 cut would be performing the swimming motions, while those behind the cut were breathing as 

 usual. This indicates a separate nerve mechanism for respiratory and locomotor activities of 

 the gills. 



Experiment XI. 



In another experiment, the cord was cut behind the second gill neuromcre, H.12. Results: 

 I. the three gills behind the cut made the respiratory movements more vigorously and frequently 

 than the two gills in front of it; and 2. the operculum and the gills in front of the cut "yawned" 

 frequently, while those behind the cut were motionless. 



II. Swimming Movements. — At no time after the operation did the gills behind the cut, 

 in experiments X and XI, perform swimming movements. The abdominal appendages in 

 front of the cut made the swimming movements often and in a normal manner. 



Miscellaneous Experiments. 



The following results were obtained at various times by stimulating the cord and the peri- 

 pheral nerves with an induced electric current. 



o. On stimulating any one of the posterior thoracic haamal nerves on the left side, the right 

 legs and the right halves of the operculum and gills were raised, the legs pointing toward the 



