ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
603 
Echinodermata, commences with discussing the relations of the Holo- 
thurioidea to the rest of the Echinodermata. 
He points out various characters which indicate the primitive nature 
of the Holothurians ; for example, the genital apparatus is not arranged 
quinqueradially, so that, whereas all other Echinoderms may be said to be 
actinogonidiate, the Holothurians are anactinogonidial ; again, they alone 
have no system of plates corresponding to those that form the calycinal 
area in other Echinoderms, or, in a word, they are non-caliculate. Part 
of the diffused nephridial system, which there is every reason to suppose 
was possessed by the ancestors of the Echinoderms, has been retained 
by Synaptids, and part by other Holothurians. Prof. Bell revives the 
use of the word podia for tube-feet, and points out (jpace Prof. Ludwig) 
that there are apodal and pedate Holothurians. 
He concludes the argument, which is very briefly stated, by remark- 
ing, “ the position, then, that the Holothurians are primitive forms, is 
spoken to (1) by the possession of characters certainly possessed by their 
ancestor, and (2) by the absence of characters seen in other Echino- 
derms, and evidently differentiations of structures developed after the 
ancestor of the Eohinodorm had become separated from the ancestors of 
other phyla.” 
The relations of the remaining Echinodermata are next considered ; 
the Cystids are recognized as the most primitive, and it is urged that 
some were probably anactinogonidial, while others had no stalk, or were 
apelmatozoic. The apelmatozoic actinogonidial Cystids divided into two 
main branches, one of which led to forms that are truly pelmatozoic, 
that is, forms that are fixed or had ancestors that were fixed — these are 
the Statozoa. The others which remain free are Eleutherozoa ; such as 
Echinoids, Asteroids, and Ophiuroids. 
The following diagram expresses the author’s views : — 
Eleutherozoa 
The Eleutherozoa either have, as in the Echinoidea, the ambulacra 
extending from the mouth to the boundaries of calycinal area, and such 
may be said to be zygopodous ; or the ambulacra are, as in Asteroids 
