460 
EDITH M. MUSGEAYE. 
The Musculature of the Stalk and Eachis. 
The musculature of the “body-wall” of Peunatulids has 
been carefully worked out by Kolliker (1872) and the 
brothers Marsliall (1882). For descriptive accounts, there- 
fore, the reader is referred to these authorities. 
In Pteroeides the body-wall is generally dense, opaque, 
and of tough, fibrous texture. In the specimens of this genus 
the musculature is correspondingly more sti'ongly developed 
than in those of Virg’ularia, Anthoptilum and Penna- 
tula. In the species “p ho sphere a” of the last-named 
genus an extreme condition in the opposite direction is 
attained, for in this form the body-wall is very feebly 
developed, and the stalk is characterised by its delicacy, 
fragility, and transparency. The musculature is, in accord- 
ance, composed of less numerous and more delicate fibres. 
In all cases the body-wall of the stalk contains two series 
of muscles : an “outer layer of longitudinal muscles,” 
and an inner layer of transverse and frequently 
circular muscles. 
The “ longitudinal muscles ” lie immediately below the 
dermis, and are composed of comparatively long muscle- 
fibres whose direction is parallel Avith the longitudinal axis 
of the colony. These muscles form a continuous layer in the 
stalk, and pass upAvards into the dorsal and Amntral portions 
of the rachis, but are discontinued laterally, the muscula- 
ture of the sides of the rachis, and particularly at the insertion 
of the leaves and pinnse, being so feebh’^ developed as to 
serve only for the protraction and retraction of the zooids, 
and can take no part Avhatsoever in the movements of the 
leaves. We have absolutely no evidence for the statements 
made by Ellis, Bohadsch, and others, of the muscular sAvim- 
ming movements of the leaves or “ fins,” as they Avere 
formerly termed. 
The longitudinal muscles of the body-Avall assist in the 
support of the colony by strengthening the tissues of the 
