ACTIVITIES. OF COLONIAL ANIMALS 509 
forms of peristalsis the waves are so slow, approximately 1.1 to 
1.2 mm. per second, that they are much more suggestive of mus- 
cular than of nervous activity. And when, as in rachidial peri- 
stalsis, the wave movement can be studied in some detail, its 
diffuse spread, its reversibility, as well as its capacity to originate 
in any isolated portion of the part concerned, all point to its 
similarity with the heart-wave in vertebrates. Like this wave, 
peristalsis in Renilla is probably primarily myogenic, but open 
to a certain degree of control from a nervous mechanism in which, 
however, the peristaltic movement does not originate. But 
whatever may be the details of peduncular and rachidial peri- 
stalsis in Renilla, it is perfectly clear that both forms of move- 
ment are purely colonial in character and have no direct 
relation whatever with the zodids. Hence the expansion and 
elevation of Renilla and its contraction and withdrawal as well 
as its locomotion are to be regarded as colonial actions probably 
of a myogenic origin and surely quite devoid of any zodidal 
influence. i 
If the waves of peduncular and rachidial peristalsis are essen- 
tially myogenic, those of phosphorescence have all the appear- 
ance of being neurogenic. ‘This is especially striking in their 
rapidity of transmission, some sixty or sixty-five times that of the 
peristaltic waves. Apparently they are the product of an unpolar- 
ized nerve-net, which serves not only phosphorescence, but also 
the general contraction of the colony as a whole and the com- 
bined withdrawal of the autozodids. These activities, though 
they involve the autozodéids, are strictly colonial, for they excite 
the withdrawal of these zoéids all together and not as individuals 
and, though they can be readily induced by stimulating almost 
any part of the surface of the peduncle or the rachis, it is remark- 
able that they cannot be called forth by stimulating individual 
autozodids. Phosphorescence, general contraction, and the with- 
drawal of the autozodéids, then, are also colonial activities, prob- 
ably dependent upon a nerve-net and certainly not involving 
the organization of the zodid. Such a nervous organization is, 
as Panceri (’71) long ago stated, social rather than individual. 
