EXPEEIMENTAL OBSERYATIOXS ON PENNATULIDS. 447 
“ The sea pens ai*e usually found on muddy or sandy sea 
bottoms, from a depth of a few fathoms to the greatest depth 
of the ocean. It is generally assumed that their normal posi- 
tion is one with the peduncle embedded in the mud and the 
rachis erect. Positive evidence of this was given by Rumphius 
writing in 1741 in the case of Virgularia rumphii and 
V. j uucea at Amboina, and by Darwin in the case of 
Stylatula darwinii at Bahia Blanca. “At low water,” 
writes Darwin, “ hundreds of these zoophytes might be 
seen projecting like stubble, with the truncate end upwards, 
a few inches above the surface of the muddy sand. When 
touched or pulled they suddenly drew themselves in with 
force so as to nearly or quite disappear.” 
“It is not known whether the Pennatulids have the power 
of moving from place to place when the local conditions have 
become unfavourable. It is quite probable that they have 
this power, but the accounts given of the sea pens lying 
flat in the sand do not appear to be founded upon direct 
observation.” 
This prone })Osition was, unfortunately, the usual condition 
of all the Pennatulids observed in captivity in the expei-i- 
menting and exhibiting tanks provided with sandy or pebbly 
bottoms in the Naples aquarium. I am also informed by 
Dr. Lo Bianco, of that institution, that specimens kept thus in 
captivity constantly remain prone, and have never been observed 
to display any of those active swimming muscular movements 
of the leaves so frequently commented upon by earlv writers. 
It is very possible that specimens described as swimming 
thus through the ocean depths have become voluntarily or 
involuntarily removed from their basal attachments, while the 
flapping movements of the leaves may have been induced by 
water currents and other mechanical external causes. They 
are certainly not induced by muscular effort on the part of the 
individual colonies. This question is further discussed in 
the present paper. 
Bohadsch desci-ibed four different movements of the 
“ leaves,” then universally regarded as flns, thus : “ They 
