Xxil THE VOYAGE OF H.M.S. CHALLENGER. 
I]. Reasons for considering previous Classifications invalid. 
As the foregoing is the latest scheme of classification, and is, in fact, the embodiment 
of all that have gone before, I propose to examine briefly the fundamental characters upon 
which it is based. 
Perrier’s classification is based upon the character of the pedicellariw. He considers 
that the pedicellariz furnish characters of the highest taxonomic value; in other words, 
he regards them as class characters, upon the modifications of which divisions of ordinal 
rank may be made. He’assigns to the pedicellarize this importance on the ground that they 
are the degenerated rudiments of organs whose functions were more important in the 
ancestral forms than those which pedicellariz now perform. Perrier states that the pedi- 
cellarize appear earlier in the embryo of Echinids than the spines. He regards them as 
more ancient organs. He rejects the view that they are modified forms of spines, as sug- 
gested by A. Agassiz. He considers that they furnish positive ordinal characters in the 
Kchinoidea. He asserts that these statements are even more clearly applicable to the 
Asteroidea than to the Echinoidea. He regards the more complex forms of pedicellariz 
as older than the simpler forms, and believes that the forcipiform pedicellariz are older 
and more typical than the more simple forficiform pedicellariz. 
Confining my remarks, to the Asteroidea, I venture to think that facts do not support 
any one of these statements, so far as that class is concerned. 
(1.) Respecting the priority of appearance in the pedicellariz and spines, I may say 
that in no starfish embryo which I have examined have I found anything to warrant the 
assumption that pedicellarie appear before spines; in fact, my observations indicate 
unequivocally that the spines are formed before the pedicellarie. In Asterias, a form 
which is crowded with pedicellarize when adult, and is one grouped by Perrier amongst 
what he considers (erroneously in my opinion) the oldest forms of Asteroidea, this is 
certainly the case. Neither has any other observer who has written upon the development 
of starfishes recorded, so far as I am aware, the appearance of pedicellarize before spines. 
(2.) As to whether pedicellarie are modified forms of spinelets, and as to whether the 
older forms of the organ are simpler or more complex than the more recent, I consider 
that those Asterids, which I believe to represent the most archaic forms, distinctly support 
the views, (i.) that the pedicellarize are modified spinelets, and (ii.) that the older forms 
of the organ were simpler and less complex than the more recent. As to the mode in 
which the more complex forms may have been evolved it is unnecessary to speculate here. 
The further outcome of the argument that the most complex form of pedicellariz indicates 
the most ancient organism would logically lead to the conclusion—although such an opinion 
is not definitely expressed by Perrier—that the Echinoidea are phylogenetically older than 
the Asteroidea, for I imagine that it will be generally admitted that the pedicellarie of 
Echinoidea are more complex than those of Asteroidea. Such a conclusion, I venture to 
