No. 3.] LIMULUS POLYPHEMUS. 439 
will be remembered the plates are divided into two divisions: 
an anterior of one plate connected with the brain, and a 
posterior of three plates separated from it. 
By laying sticks across the appendages of such an animal it 
is forced to exercise its muscles. For, in endeavoring to 
remove the annoyance, it continually strikes against the sticks 
with its appendages and with increasing efforts. 
Before the exercise both divisions made on an average 
twenty-three inspirations a minute. After an hour’s exercise 
the anterior as well as the posterior division made on an 
average twenty-seven a minute, showing that exercise increased 
the respiratory activity of each plate, and to the same extent. 
Other Limuli were treated in the same way and with the 
same result. 
(2) It was of special interest to see whether a nervous 
stimulus influenced the rate and extent of the plates alike, 
when they were divided into two divisions, by lesion between 
the second and third ganglion. 
When the animal was quiet one person timed the inspiratory 
acts of the anterior, at the same time another noted those of 
the posterior division. The result was that for every observa- 
tion the posterior and anterior made about an equal number of 
inspirations in the same time and with the same extent. This 
was repeated several times with like result. 
After that, the different appendages were pulled, so that the 
Limulus became greatly irritated. The plates anterior to the 
lesion made exaggerated inspiratory movements, just as all the 
plates of a normal Limulus would if thus treated. On the 
other hand, the plates posterior to the lesion but slightly 
increased their extent. 
In one case the anterior made thirty-one, while the posterior 
division only made twenty-one inspirations during the same 
space of time. The result was the same with slight differences 
each time that the observation was made. 
This might have been expected, because the anterior division 
being connected with the central nervous system would be 
affected by every cerebral impulse, while the posterior, which 
is separated from it, could not be so influenced. 
