io6 Natural History Bulletin. 



All these muscles are composed of nucleated non-striated mus- 

 cle fibers. 



Where there are undoubted muscle fibers, one naturally 

 looks for nerve-cells or fibers. They have not been seen in 

 any of my sections of this species. There is evidence that 

 they exist, however, aside from histological evidence. For 

 instance, if one touches the tip of a branch of a large zoantho- 

 deme bearing living polyps expanded, he will find that a wave 

 of retraction is started from the point touched and proceeds 

 rapidly down that branch to where it joins other branches, 

 when the wave starts iij^ tliese branches, and finally reaches 

 to the polyps the most remote from the starting-point. The 

 stimulus is conveyed from polyp to polyp and each responds 

 by retracting. The stimulus, furthermore, is evidently con- 

 veyed through the mass of the coenenchyma or else through 

 the ectodermal investment common to polyps .ukI zoantho- 

 deme! Which of these is the true medium, could easily be 

 ascertained by "girdling" a live specimen and then seeing 

 whether or not stimuli could be transferred. Ii seems not 

 unlikely that the ccenenchyma is traversed by fibres which 

 serve as nerves whether they can be histological!}- classed as 

 nerve tissues or not. 



Spicules. These are of rather small size, purple, pink or 

 white, and vary considerably in shape. Perhaps the most 

 common form is what VVm. S. Kent calls fusiform tuberculate 

 (PI. I, figs. 15, 18), but arcuate, bi-, tri-, and quadri-partite 

 spicules are met with (figs. 12, 16, 17, 21, 23), as well as 

 such unsymmetrical forms as the one illustrated in 'Kig. 22. 



The most striking characteristic of the spicules of this 

 species, and one which I have not found elsewhere, is the fact 

 that each spicule seems to be composed of two halves divided 

 by a plane passing along the longitudinal axis of the spicule. 

 The halves seem to be opposed to each other by flat faces 

 like the halves of a bean. In fig. 14, PI. I, the plane of 

 juncture is indicated by a longitudinal line, and in fig. 24 

 it is indicated by a line passing through the long diam- 



