808 DR. E. B. WILSON ON THE DEVELOPMENT OF RENILLA. 
[ Appendix.—During the passage of this paper through the press, I have discovered 
in several genera of Alcyonaria that the dorsal filaments are, in fact, ectodermic 
downgrowths from the stomodzum, whereas the six others are strictly entodermic 
structures. My failure to recognise this fundamental difference was due to the 
circumstance that the entodermic filaments become at an early stage perfectly con- 
tinuous with the stomodzeal ectoderm, like the dorsal filaments, and my most 
favourable sections happened to be in every case through the entodermic filaments. 
For a description of these new observations I must refer to a forthcoming paper 
in the ‘ Mittheilungen aus der Zoologischen Station zu Neapel.’—Naples, September 
20, 1883.] 
EXPLANATION OF FIGURES. 
The following lettering is used uniformly in all the figures. Other reference 
letters are explained for the separate figures. The figures of sections are with a few 
exceptions drawn with the camera. Those of the segmenting eggs and of the external 
appearances of the colony are free-hand. 
al. Gastric cavity. 
ax. Axial cells of peduncular septum. 
C. Central cells. 
cm. Circular muscles. 
ch. Radial chamber. 
cx.  Calyx-teeth. 
d.c.z. Dorsal calyx-tooth. 
d.l.ch. Dorso-lateral chamber. 
dl Dorso-lateral mesenterial filaments. 
d.l.s, Dorso-lateral septa. 
d.s. Dorsal septa. 
df. Dorsal mesenterial filaments. 
e. Free edge of peduncular septum. 
ec, Ectoderm. 
en. Entoderm. 
ex. Exhalent zooid. 
ie Mesenterial filament. 
Im. Longitudinal muscles. 
@. (Esophagus. 
p\. p®., p®., &e. Sexual polyps, or buds destined to become such, numbered 
in the order of their appearance. 
ped. Peduncle. 
