33 
etc., and probably all the polyporous forms will prove to have the 
proximal ambulacral plates oligoporous. As I have explained in 
my "Ingolf" Echinoidea I, p. 132, there appears to be a universal 
tendency towards the development of a greater number of tubefeet, 
and this is reached in two different ways, viz., by the disappearance 
of the primary tubercle on some of the ambulacral plates, which 
then become very low and numerous (for instance, Tripneustes, 
Holopneustes) , the plates remaining oligoporous; or the same end 
may be reached by the plates becoming polyporous. Both these 
features appear to have developed along several different lines. 
Lastly, when Lambert designates the differences in the 
microscopical structures of pedicellariæ as ”relative”, I must protest. 
Whether for instance the blade of the valves of globiferous pedi- 
cellariæ is a closed tube ending in a single, terminal tooth, or is 
Open, with a series of teeth on either side, or with a single un- 
paired one below the end tooth — I wonder how these can be said 
to be relative differences; or whether the spieules are dumb-bell 
Shaped, or bihamate, or quite irregular — to call such differences 
relative seems really curious. On the other hand, some of the 
characters afforded by the structure of the test may correctly be 
designated as relative, for instance the dimensions of the coronal 
plates, the depth of the gill-slits, the more or less parallel condi- 
tion of the arcs of pores. Of course, I do not wish to maintain 
that such characters must not be used, because they are relative; 
I only wish to protest against designating the microscopical struct- 
ures as such, thereby implying one more reason against their value 
in classification. On the contrary, it may be stated that these 
characters have the advantage .of not being so relative as are 
Several of the characters derived from the structure of the test, 
and nobody, I think, will deny that it is much easier to use such 
definite characters than such relative characters as for instance 
the dimensions of plates, which may even vary considerably 
with age. 
I have already once before ("Ingolf” Echinoidea II, p. 26) 
3 
Vidensk. Meddel. fra den naturh. Foren. 1910. 
