THE AMERICAN LOBSTER. 
129 
nent nucleus at the peripheral end of this cell, there are two other bodies — one near the 
tubular neck — which take up the stain like nuclei and are considerably refractive. 
From the larger end of the cell (fig. 206) a slender process is given off (compare figs. 
201,204 from the maxillae), which suggests a nerve fiber. All that I can say definitely 
is that this process is in continuity with the cell, probably with its wall. I did not see 
many cases of a similar character. 
EXPERIMENTS UPON THE SENSORY AREAS OF THE BODY AND APPENDAGES. 
Before discussing the function of the tegumental organs in general, I will record 
some experiments which were made to determine how the lobster reacts to stimuli 
directed against the dead shell or cuticle. 
The lobsters experimented upon were taken from the sea, placed on their backs 
on a table, and allowed to remain in this position until quiet. At first they move 
their appendages vigorously in trying to right themselves, but soon come to rest. By 
sprinkling them with sea water they may be kept fresh for experiment for a consider- 
able time. 
Y arious stimuli . such as electricity, heat, weak acetic acid, ammonia gas, clam juice, 
were applied to different parts of the body, with a view to ascertain the most sensi- 
tive areas where the quickest and most vigorous responses were given. 
The degree of sensibility to external stimuli is surprisingly great in many cases, 
where the skin of the lobster with its shelly covering seems quite as sensitive as that 
of the frog. In other cases, liowever, the animal is much less responsive, a fact which 
we may attribute in some degree to the thickness of the shell. 
To sum up the experiments in a general way, all or nearly all the appendages 
react strongly to chemical stimuli, and in many cases the surface of the body is 
capable of receiving and responding to stimuli of various kinds. If a jet of ammonia 
gas is injected against the intersegmental membranes or appendages of the ‘‘tail,” the 
pleopods may be set in very lively motion and violent flexion of the whole abdomen 
may follow. Direct the jet upon the anterior swimmerets, and the last three pairs of 
walking legs are drawn backward and make scratching movements to remove the 
offending object, reminding one of the motions of a ‘‘reflex frog” when its skin is 
stimulated in a similar way. 
The reaction is more violent when the stimulus is applied to the swimmerets than 
when directed against the intersternal membranes. The seminal receptacle is very 
sensitive, and when stimulated the walking legs make violent scratching movements 
toward it. If the jet of gas is directed along the surface of the walking legs, the 
reaction is usually greatest at their tips. 
If the extremities of the large eh eke, especially the propodus, are touched by the 
gas the claw opens and shuts. The first pair of antenna?, are much more sensitive to 
the stimuli than the second pair. If the jet is directed over the region of the mouth, 
very violent chewing movements are set up. 
If the ammonium vapors be squirted on the dorsal .surface of the carapace or 
abdomen, a vigorous response is sometimes seen by the immediate movements of the 
legs. Both males and females respond to the ammonia stimulus on the abdominal 
appendages and intersegmental membranes. 
Very similar reactions are obtained if a small piece of blotting paper wet with 
weak acetic acid is used. In some cases no response is obtained if the wet paper is 
F. C. B. 1895—9 
