THE DIGESTIVE ORGANS OF THE ALCYONARIA. 829 
1903 numerous feeding experiments were carried out at the 
biological station of Port Erin on the British Aleyonium 
digitatum. These yielded very interesting results which 
are briefly described.} 
I have examined the plexus of mesoglceal cells of 
Alcyonium, hitherto regarded as a nerve plexus, in the 
living as well as in the preserved condition, and after a careful 
comparison with other Alcyonaria, have come to the conclusion 
that it can be no longer regarded as a differentiated nerve- 
plexus. We have at the present time no experimental 
evidence of the existence of a specialised nervous system in 
the Alcyonaria. 
THE Zooips. 
In form, and to a very considerable extent also in structure, 
a zooid of the monomorphic Alcyonium is very similar to a 
fully-developed autozooid of the dimorphic Sarcophytum 
and Lobophytum. 
The zooids vary considerably in size. As they are extremely 
contractile it is frequently impossible to form any true con- 
ception of their actual size from preserved specimens. Forms 
inhabiting tropical waters, however, frequently have smaller 
and fewer zooids than their relations in temperate seas. 
The fully expanded living zooids of Aleyonium digitatum 
are usually very different in form, size, and apparent structure 
from those in the preserved condition. 
A fully-expanded living zooid of Aleyonium digitatum 
frequently measures from 6—9 mm. across the crown 
of tentacles, and the anthocodia often attains a length of 
from 10—12 mm. ‘The tentacles are from 3—6 mm., and the 
pinnules about *5 mm. in length. 
1 These experiments have been repeated on several Alcyonaria, including 
Corallium rubrum, and in Actinians, including Anemonia suleata, 
at the Zoological Station at Naples during the month of April, 1905. The 
results of these experiments confirm the observations recorded in the presen 
paper. 
