Behavior of Tubicolous Annelids 169 
lessness involved were such as to preclude anything like simple 
or direct reactions to any given stimulus. In other words, the 
conditions involved the operation of a complex of peculiar and 
anomalous stimuli, so that the reaction to the shadow stimulus 
was only one of several acting upon the creature at a given time, 
However, taking a specimen when less disturbed by promiscuous 
movements of the body it was found that a sudden shadow often 
caused a sudden response, or jerk of the body, and a correlated 
contraction of the gills. This might recur upon a second, or even 
a third test, but after that it became practically indifferent. Re- 
peated after an interval of a few minutes a similar reaction was 
liable, but failure was also frequent. Excision of the gills of such 
specimens was invariably followed by total absence of photic re- 
action, and fully confirm the earlier experiments and conclusions, 
Some connected account of the facts portrayed in the several 
tables in addition to references made at various places in the paper 
may make clearer their significance and importance. Incidentally 
it may be stated that these data are but a small fraction of a very 
large number of observations made during two successive summers. 
To attempt to include all would unnecessarily cumber the paper 
with details which, while not without some value, are not vital 
to the fundamental aims of the investigation. 
Tables I and II show records of two series of specimens: A B 
CDE and HI J KL. Both were from deep water, eight to 
fifteen fathoms, and show a fair average of reaction of specimens 
from this environment. ‘The records are specific, that is, made 
from definite individuals. The really significant feature of these 
records is their almost exclusively negative character. An inter- 
esting detail of Table I is the zero record of specimen C, quite 
marked in the first, or 11 o’clock test, and its almost exclusively 
zero record for the 2 o’clock test. In this respect the record is 
somewhat unusual. A specimen may often exhibit such a be- 
havior at one time and an altogether different aspect at a subse- 
quent test. 
In marked contrast with the foregoing is the record shown in 
Table III. Another series of five specimens, A B C D E, taken 
from shallow habitat illustrate what hundreds of similar tests of 
