No. 3.] LIMULUS POLYPHEMUS. 437 
activity of the corresponding gill-plate ; and, provided that the 
ganglia of the cord are left intact, while the remainder of 
the central nervous system is destroyed, the respiratory move- 
ments are not abolished. This of itself is enough to show 
that the ganglia of the cord include the chief centres of 
respiratory movements. 
(¢) The fourth ganglion (consisting in the adult of the 
fourth, fifth, and sixth united) was cut through longitudinally, 
so that the nerves of the left and right sides were left attached 
to their respective halves. Several hours after the operation, 
although both sides of the fourth and fifth plates began inspir- 
atory activity together, the left moved more anteriorly and 
with greater extent than did the right sides, and in the expir- 
atory phase they did not move so far posteriorly. Occasionally 
the left sides had cramp movements, while the right were 
moving normally, and this was often followed by cramp move- 
ments of the right sides, during which the left sides moved on 
uninterruptedly. Besides these many other observations were 
made on Limuli operated in this way. They strengthened the 
conclusion that each half of a ganglion controls, to a certain 
extent, the function of its own side. 
F. Experiments on the Peripheral Nerves. 
The following experiments were made to ascertain the func- 
tion of the anterior and posterior nerves. As was said before, 
the anterior nerves send fibres to the integument, and the 
posterior to the gill-plates. 
(2) The posterior nerve was exposed, ligatured in two places, 
and cut between the ligatures. 
Each time that the distal end was stimulated with induction 
currents of moderate intensity, that half of the gill-plate 
to which the nerve was attached made inspiratory move- 
ments. Neither the appendages, abdominal carapace, nor 
other plates moved. Therefore, the posterior nerve contains 
motor fibres. 
() When the electrode was applied to the proximal end of 
