65 
Length of the spines. This value, which is one of the least useful of the former 
specific characters, varies in a high degree round 60 ix (30—80 ( u). Very large deviations 
occur as follows : 
90 [X IV; 80 - 15O [X XXXVII; 120 - 155 u. XX; IOO- 200 [X XXXIV; I50 [X XI, 
XXIII, XXIV, XXV, XXVI, XXVII; 150—200 n XXXIII. 
A sharply defined limit is nowhere to be observed and it would be an arbitrary pro¬ 
ceeding to decree that with some ten p. more or less a new species appears. 
Shape of the spines. Here also the differences, which may occur, are very slight. 
The shape, which is the most frequent, is as follows: triangular, with the distal side somewhat 
steeper than the proximal side; a smooth surface; inserted at right angles with the axis. Small 
deviations may occur, viz. a more acute top; an elongated base; distal side more at right angles 
with the axis; the entire spine more distally inclined. Of greater importance are the more 
heavily built spines of X p and especially of IV a and [ 3 , and XX; a granulated surface is 
present in VIII and XXV. However these differences are not very large and neither of them 
are of specific value, especially if one keeps in mind the very great variability of these charac¬ 
teristics in Stichopathes- species, where I could examine them closer. 
Mutual distance of the spines. This value, which already is very variable, from 
210 tx —375 [x with all possible transitions, shows the following larger deviations: 
400 [x: XXX and XXXII; 450 { x: XXXIII; 570 p.: XXIII; 600—700 p.: XXXIV; 
750 p.: XXVII; 1000 p.: XXIV (old branch) and XXXVII. 
A diminished value show: 195 p.: VIII; 180 p, : XIX; 100 p,: XXXV and XXXVIII. 
Very large leaps occur only from 800—1000 p., although it is not impossible that in 
XXIV on younger branches the spines are more crowded; at all events this difference is less 
than the individual variability in various cases. 
Distribution of the polyps. In this respect there are only very slight differences. 
The polyps are always inserted in a single series; very slight deviations of this rule occur only 
in IV (on the oldest part of the colony), X and XXIV. In five cases the polyps are inserted 
on one special side of the colony; in 22 cases there is no preference for a special side. 
Dimensions of the polyps. This value, which obviously is very dependent on the 
preservation of the polyps, is unequal for nearly every described specimen. Very great deviations 
I find by XXIII, while the demensions of XXXIII, XXXV, XXXVII and XXXVIII form an 
almost imperceptible change towards the normal middle value. 
Difference between the proximal and distal pairs of lateral tentacles. 
This difference may be observed in greater or lesser degree in nearly all polypbearing specimens. 
It is small but clearly visible in I, XII, XV, XXI, XXXII, XXXIV, XXXV and XXXVII, 
while the difference is entirely absent in V (or very slight) XIII |3 (a shows a great difference!) 
XVII, XX, XXIII, XXIV, XXX (except in some polyps), XXXIII, XXXVIII. The remarks 
between brackets show already that only in a few cases an entire equality appears; the case 
of XIII a and |3 shows besides how nearly related specimens, found in the same locality 
and otherwise entirely alike, are very different in this respect without allowing a specific 
difference. — Besides the degree of predomination ol the proximal lateral tentacles is very 
9 
SIBOGA-EXPEDITIE XVII. 
