No. 3.] LIMULUS POLYPHEMUS. 435 
10.10 A.M. 22 inspirations in 60 secs., cramp movement, 60 secs. 
10.12 ‘“c 30 “ “c go “ “ 73 75 73 
10.143 6“ Zc “se 6c 60 66 79 6“ 75 66 
10.16 “ 3 “ ““ 30 “ ‘“c 66 45 ‘““ 
10.174 “c Bhs “c“ 6c go 6 “cc 6c 60 6c 
10.193 66 34 ““ “ go 73 ““ 6c 75 66 
During the next two weeks the respiratory activity did not 
vary much. 
(2) The abdominal cord was cut transversely between the 
operculum and the first ganglion (7 Fig. 1). In some Limuli 
the mechanism did not differ from that of the above. In 
others the respiratory movements were very slow immediately 
after the operation. The following day they became inter- 
mittent, that is, they alternately ceased for a time, then 
returned at times above, at other times below the normal, 
and occasionally cramp movements appeared. Several days 
later, as the animal weakened, the respiration gradually 
ceased. 
The gill-plates all move in the same rate, extent, and rhythm, 
and have cramp or interrupted respiratory movements at the 
same time. 
(c) When only the artery that ensheathes the cord is cut, and 
not the nerve, allowing a loss of much blood, with the excep- 
tion of short periods of cramp or no movements, the respiratory 
mechanism of Limulus is not altered. 
(Z) In another series of experiments, the cord was cut 
between the second and third ganglia (II and III, Fig. 1). 
Thus the gill-plates were divided into an anterior division of 
two plates, still connected with the brain, and a posterior 
division of three plates separated from it. In some cases, 
for the greater part of the time the anterior division moved 
quite normally. The posterior division part of the time made 
slow movements that alternated with cramp movements, about 
as noted below :— 
4.45 P.M. 17 inspirations in 35 secs., cramp movement, 60 secs. 
4.46 “““ 22 ““ “cc 50 6“ 6“ ““ 60 6“ 
4.484 6“ 26 “c“ 6“ 55 6“ 6“ 6“ 55 6“ 
