I IO 
with the dimensions twice as small as in the first type; the tentacles are shorter in the same 
proportion. Both types alternate regularly, with an interpolypar distance of 2 to 3 mm. Sometimes 
the small polyps are absent and the interpolypar distance of the larger polyps is in this case 4 mm. 
On closer inspection of the most typical characteristic, viz. the shape and the arrange¬ 
ment of the polyps, it must be remarked that: i° the alternation of the larger and smaller 
type of polyps is not regular, as is mentioned by Roule himself, who says that on some parts 
of the colony only the larger type occurs, with a somewhat greater interpolypar distance, and 
smooth coenenchyma between the polyps, 2 0 a regular alternation of larger and smaller polyps 
occurs repeatedly in many other species (also among the Siboga-material), but very rarely on 
the entire colony, and also a more irregular alternation is present, e. g. two small ones, one 
larger one, etc., together with a regular alternation on other parts of the same colony, or a series 
of larger polyps only, 3 0 the two subtypes of larger polyps, viz. one with radiate tentacles and one 
with the tentacles in three pairs, the latter of which types is present on the higher parts of 
the colony, may be explained by the available room on the axis ; as long as the axis is young 
and slender, the polyps are forced to arrange their tentacles in pairs, while on the older and 
thicker parts of the axis the tentacles have more room and can be arranged in a radiate 
manner; the radiate tentacles indeed appertain to polyps, which once, in a younger stage of 
the colony-growth, were themselves inserted on the top of the colony and in their turn had 
their tentacles arranged in three pairs; 4 0 the small polyps have, even on the higher parts of 
the colony, always a radiate arrangement of the tentacles, since there is room enough for them, 
where the twice larger polyps are coerced by the diminishing room to arrange their tentacles 
in pairs; 5 0 the smaller polyps have the same shape and structure as the larger polyps, only 
on a twice smaller scale, and since there are parts of the coenenchyma, where there is no trace 
of the smaller polyps, it is obvious that the small type is only a young individual from the 
larger (adult) type; they are young polyps, alternating more or less regularly with the adult 
ones, as was repeatedly found by me in other species and genera ; probably the coenen- 
chymal parts without small polyps are going to have them. This interpolypar growth of the 
colony is often to be found together with the apical growth. As type of polyp, characteristic 
for Stichopathes dissimilis R., we should consider Roule’s larger type of polyps, with 
a radiate arrangement of the tentacles (Roule: 14 pi. VI, fig. 3). — Concerning 
the spines the following remarks may be made: the very variable mode of arrangement of the 
spines on one and the same colony is frequently to be met with in various, very diverging 
species in a greater or lesser degree, without it being possible to look upon it as a typical 
characteristic. The arrangement, as it is figured by Roule on his pi. VI, fig. 2 a, although 
embracing only the smaller part of the colony, appears to me as the normal condition, which 
ought to be characteristic, and from which the other arrangements may be derived. — I myself 
have found again and again colonies with a regular distribution of the spines, while some specimens 
of the same species showed an irregular distribution over a great distance through shifting of the 
spines, torsion of the axis, and such reasons. The normal condition of the spines in Stichopathes dis¬ 
similis R. is in my opinion : 5 —6 longitudinal rows, alternating in a quincunx ; length 250 to 400 p.; 
mutual distance ± 500 p. ; acute conical shape, at right angles with the axis ; smooth surface (?). 
