No. 3.-] LIMULUS POLYPHEMUS. 443 
even when divided into two divisions by lesion, is the same. 
The rate may be changed by exercise, but the change will still 
be the same for both divisions. 
On the other hand, the extent and rhythm of the different 
divisions of plates is different, because the division connected 
with the brain is influenced by the latter, while the posterior 
is not. 
III]. GENERAL OBSERVATIONS. 
In studying the behavior of the Limuli that had been 
operated, many peculiarities were observed, of which it was 
thought worth while to mention the following : — 
(a) If we extirpate half of the brain of Limulus (& Fig. 1), 
after several hours we find that it has lost some of its normal 
habits. When it is placed in the sand it no longer burrows 
in it, nor does it turn on to its ventral side, or turn its spine 
forward when irritated while on its back. 
Furthermore, its appendages are asymmetrically bent on 
themselves, on the side opposite to the one operated (Fig. 2). 
That is, they are bent on themselves so as to make a small 
angle between the third and fourth segment. The appendages 
on the side operated are not changed. As a consequence, the 
animal now moves in a circle toward the uninjured side. This 
movement, as well as the inability to turn on its ventral side, 
lasts about two months, then gradually passes off. 
(6) If more than half of the brain is removed, the results 
are about the same as those above, with the exception that the 
gill-plates as well as the appendages of one side were asym- 
metrically held, with relation to the side of the brain most 
injured. The animal had forced movements to that side of the 
brain left uninjured, and at rare intervals one side of the gill- 
plates was inactive. At the end of three months the so-called 
forced movements still persisted. More than three months after 
the operation, Limulus was chloroformed and dissected, when 
an astonishing fact was discovered. It was seen that nerves 
which ran to the anterior integument from the brain, and that 
were cut in the operation, had regenerated and grown to a bit 
of nervous tissue left attached to the collar. 
