450 LESLIE B. AREY AND W. J. CROZIER 
9 : 55 The two animals turned and went directly back toward their 
nest. The solitary one, two feet away, turned back at about 
the same time. 
10:06 All three reached entrance of the nest, by a straight route in 
each case. 
April 16, 191S. Dyer Island. 
Low tide 5:30 p.m. Several rocks some feet from the main shore- 
line, on the southern side of Dj^er Island, afforded convenient sta- 
tions for stud,y of Onchidium colonies occurring more closely grouped, 
on the whole, than was the case on Little Agar's. At the top of one of 
these rocks there was a single colony, well removed from the closely 
clustered nests around the lower edge of the rock. At 4 : 46 the mem- 
bers of this topmost group began to emerge ; by 4 : 53 the whole colonj^, 
numbering 17 individuals, 3 to 13 mm. long, had emerged. They scat- 
tered in various directions over the rock; some going 70 cm. away from 
the nest entrance. No animals from other nests became mingled with 
them. By 5:37 one Onchidium of this group had turned and begun 
to creep toward home; at 5:48 the last one of the 17 had done like- 
wise, the whole number finally arriving at the entrance to their nest 
by 5:55. 
Hirasaka ('12) has noted that the Japanese 0. verriiculatum 
Cuv., though easily obtainable at low tide, seemed at high water 
to have 'disappeared.' He also records that this species is not 
seen, even at low tide, during stormy weather, and suggests that 
the animals retire to clefts in the rocks. This corresponds to 
the behavior of 0. floridanum, with the difTerence that in stormy 
weather this species does not emerge from its nests on a given 
bit of shore if the latter be exposed to wind or surf. Rain or an 
overcast sky has a negligible effect, if indeed any at all, upon 
the emergence of the Onchidia. It is stated that O. verrucu- 
latum is most abundant from April 15th to October 15th, and 
Hirasaka suggests that this species, like other pulmonates, passes 
through a period of hibernation (also Fujita, '97). 
0. floridanum, in the warmer Bermuda region, does not hiber- 
nate although some of our field notes suggest that on some of 
the colder winter days the animals may fail to emerge. Further 
observations would be necessary to settle this point. 
The intertidal rock crannies inhabited by Onchidium celticum 
were carefully described by Joyeux-Laffuie ('82), who detected 
also the fact that these animals ''abandonnent leur retraite en 
moyenne une heure ou une heure et demie apres que la mer a 
