NOTE ON SARCODICTYON. 165 



found was the case with the Loch Fyne specimens in 1883, 

 but that there are two distinct tints of yellow colony, one 

 paler and greyer (PL VIII., fig. 2) in which the spicules 

 are all colourless and the yellowish tint is merely due to 

 the superficial tissues (chiefly the ectoderm) of the polypes 

 and stolon, and the other of a much richer yellow (PL 

 VIII., fig. 1), with sometimes a tinge of orange, and in 

 these most of the spicules are very distinctly of a yellow 

 colour, even when seen singly in thin sections (PL VIII., 

 figs. 6, 7, 8), and when in mass along with the soft 

 tissues they make up the rich yellow seen on the outside 

 of the colony. The spicules which are yellow in these 

 cases are exactly the ones which are red in the red 

 colonies, viz., those of the stolon and of the lower thick 

 opaque part of the body-wall, leaving those of the upper 

 translucent part of the body-wall and of the tentacles 

 colourless (see PL VIII., fig. 7). I succeeded in keeping 

 yellow colonies, of both tints, alive and fully expanded in 

 the aquarium at Port Erin for some time last summer. 

 The upper parts of the body wall and the tentacles are 

 exactly like those of the red form (see PL VIII., figs. 4, 5). 

 Consequently, there are altogether three colour varieties 

 of Sarcodictyon which I know of : — 



1. The red form, with red spicules in the stolon and 



lower part of the polype ; 



2. The bright yellow form, with yellow spicules in 



the stolon and lower part of the polype ; 



3. The pale yellow form, with colourless spicules 



throughout the colony. 



All of these usually have the polypes in single file, but 

 any of them may exceptionally have the polypes grouped 

 in little clumps (as in PL VIII., fig. 1). Consequently, 

 the characters distinguishing Sarcodictyon agglomerata 



