Professor Herdman on the Structure of Sarcodictyon. 37 



Yig. 14 in PL I. shows a transverse section through the lobes. 

 The grooves between these lobes are in some specimens con- 

 tinned down the side walls of the body, so as to be visible in 

 profile view as lines extending nearly to the base (PL I., 

 Fig 5). In a specimen not quite so much contracted as the 

 one shown in Fig. 6, the terminal aperture was wide, the 

 lobes were very regular, and a colourless mass, formed by the 

 upper part of the body bearing the mouth and the tentacles, 

 was visible in the aperture between them (see PL L, Fig. 7). 

 Consequently, the terminal aperture in Figs. 5, 6, and 7 is not 

 the mouth opening, but is merely the termination of the non- 

 retractile side walls of the body. 



This non-retractile part of the body is, like the stolon, 

 coloured either dull red or pale yellow, according to the 

 variety, but the retractile region above is either much paler 

 and more transparent, or usually quite colourless.^ It is 

 shown in PL I., Fig. 8, which has been constructed by com- 

 bining portions of two or three partially expanded polypes. 

 Its upper end bears the mouth, surrounded by the eight com- 

 pound tentacles, which seem to have a slight web uniting 

 their bases, the result being that the body seems in profile 

 view to expand slightly at its upper end. 



The tentacles (PL I., Figs. 8-11) are not long (2 to 2-5 

 mm. in length), and are broadest about half-way up. They 

 taper to a rather blunt point at the tip. In one or two 

 cases (see Fig. 11) the tip is bifurcated. Short stumpy pinnae 

 are borne on the sides of the tentacles ; there are from 10 to 

 20 of these pinnae upon each side, 14 to 16 are usual 

 numbers. They are largest on the wide central part of the 

 tentacle, and decrease in size towards the base and the tip. 

 There are usually three or four pairs of very short pinnae at 

 the base of each tentacle (see Fig. 9). 



A. — Anatomy. 



The general anatomy of each polype is of the ordinary 

 Alcyonarian type. The mouth, which is placed on the sum- 



1 In one specimen of the ordinary red variety I noticed that the tentacles 

 and upper part of the body were slightly but distinctly yellow, thus forming 

 an interesting transition to the yellow variety with colourless spicules. 



