32 
noidea” and in Delage and Hérouard's "Traité de Zoologie Con- 
eréte” Vol. III. (p.221—246). In fact it is mainly among the Echinina 
that I find pedicellariæ and spicules of use for characterizing so large 
groups as families; in the other larger divisions I generally find 
these structures to be only of specific or generic value. The Echi- 
nina, however, afford in general, in the structure of the test, so 
very little diversity and such insignificant differences that it would 
in certain cases be impossible to refer even to the family the 
naked tests alone. But here the pedicellariæ and spicules have 
been wonderfully diversified, and anybody who has made a thorough 
study of these forms, not of the naked tests alone, must agree that 
these structures afford a most excellent basis for classification; it 
must likewise be agreed that the classification based on these struct- 
ures: evidently does not separate closely related forms. On the 
contrary, forms which are seen from the test structure to be obvi- 
ously closely related, for instance those with deep mouth-slits or 
the transversely elongate Echinometrids, are also found to be com- 
pletely in accord in regard to the microscopical features of the 
pedicellariæ and spicules. One feature alone seems to stand in 
contradiction to this, viz., the number of pores. It is true that if 
the character of the oligoporous or polyporous condition is taken to 
be of primary classificatory value, then the microscopical structures 
are not in accordance with it; but in that case other important 
structural features of the test also, e. g., the deep gill-slits, must 
be disregarded, as it has been, indeed, in the other elassifications 
(Revision of Echini, etc.). I think, however, it cannot be doubted 
that the polyporous condition has developed along several different 
lines. We know a polyporous Echinothurid, Pe/anechinus, a poly- 
porous Arbaciid, Tetrapygus (which has for a long time been con- 
sidered as belonging to the otherwise oligoporous genus Arbacia) 
that this special form of globiferous pedicellaria has been developed 
along different lines, occurring for instance also in some Temno- 
pleurids; this, however, does not ilten the fact that it mads one 
of the chief characters for the family of the To 
