342 EDITH M. PRATT. 
We have, therefore, no evidence in favour of Wilson’s 
hypothesis of an ancestral identity of form, origin, and 
multiple function of the dorsal and ventral mesenterial 
filaments. 
The ventral mesenterial filaments of the Alcyonaria 
exhibit considerably more variety in form, size, and, to a 
certain extent, in structure than do the dorsal filaments. 
In his account of the anatomy of Coenopsammia Stanley 
Gardiner (1900) maintains that the mesenterial filaments, 
together with the stomodeum, are ectodermic in origin in 
that form, and says: 
“The stomodeum of the Zoantharia, and necessarily also 
of Alcyonaria, is not comparable to the stomodzum of the 
Triploblastica, but rather is, with the mesenterial filaments, 
the homologue of the whole gut. The so-called endoderm, 
giving rise to the muscular bands and generative organs, and 
performing also the excretory functions, is then homologous 
with the mesoderm of Triploblastica. In the terms of the 
layer theory, of whatever value it may be, the Actinozoon 
polyp must then be regarded as also a Triploblastic form 
having ectoderm, endoderm, and mesoderm.” 
E. B. Wilson (1884, p. 7) states in the development of 
Funiculina that the ventral mesenterial filaments arise 
quite independently of the stomodeum, and are endo- 
dermic inorigin. What Wilson has shown for Funiculina 
may be true of other Alcyonaria. I have already shown 
(fig. 8) that the ectoderm terminates with the aboral opening 
of the stomodeum in the adult condition, and only the 
mesoglceal and endodermal tissues are continued downwards 
into the mesenteries. Yet a histological study of the mouth 
disc, stomodzeum, and ventral mesenterial filaments in several 
members of the family reveals many points of similarity, if 
not identity, in their elemental constitution. Both granular 
and mucous gland cells, as well as nematocysts, occur in all 
these structures. 
Milne-Edwards in 1835 was the first to attribute a digestive 
function to the mesenterial filaments of the Alcyonaria,. The 
