ACTIVITIES OF COLONIAL ANIMALS 503 
spontaneous response of the neighboring zodid itself and not due 
to transmission. Even the decapitation of a zodid with a pair 
of sharp scissors and the subsequent vigorous contraction of the 
remaining stump does not seem to affect the neighboring indi- 
viduals. In a similar manner when one autozoéid or a group of 
such individuals is fed with minute bits of crab meat or with 
tow, the zodids directly concerned open their mouths, but the 
neighboring ones do not so respond. Asa result of many tests 
of this kind I have come to the conclusion that, though auto- 
zooids are freely open to individual stimulation, they of them- 
selves are not centers from which impulses pass with any degree 
of freedom to neighboring zodids or to the colony as a whole. 
Although an autozoéid cannot be said to be a center from which 
impulses pass freely to the rest of the colony, impulses from the 
general colony reach the autozoéids with great ease. Thus if the 
distal tip of the peduncle or the dorsal surface of the rachis of 
an expanded Renilla is touched with a rod, the whole assemblage 
of autozodids will quickly withdraw, an operation which is very 
much less likely to happen when the stimulus.is applied to the 
root of the peduncle or to the ventral surface of the rachis. A 
faradic current applied to the tip of the peduncle or to the 
rachis also induces a general withdrawal of autozodids. These 
conditions show clearly that stimulation of parts of the colony 
other than the autozodids readily excites impulses that reach 
these polyps, notwithstanding the fact that the converse of this 
can scarcely be said to be true. 
Effective stimuli applied to the tip of the peduncle and to the 
rachis are not only followed by the withdrawal of the autozodids, 
but also commonly call forth more or less general contraction of 
the whole rachis, a reaction which can likewise be induced by 
very intense artificial illumination such as that from a powerful 
arc-light. 
This general contraction may result in a discharge through the 
axial pore of some of the water contained in the colony, but it 
usually sooner or later passes off and the colony quickly refills 
itself. The general contraction just described must be due to 
the activity of the rachidial musculature as a whole, and when 
