18 Ech . 
ECHINODERMATA. 
circumoral tentacles, But not always into ‘‘ podia ” (tube-feet) ; (7) there 
is no ovoid gland ; and (8) the larva and development is less complicated 
than in other classes. All other Echinoderms were caliculate, but many 
Cystidea appear to have been anactinogonidial, and some Oystids were 
probably never fixed, and without fixed ancestors (“ apelmatozoic ”). 
The apelmatozoic actinogonidial Oystids lead, on the one hand, to the 
true pelmatozoic forms, in which the oral surface looks upward (“ Stato- 
zoa ”) ; on the other hand, to the Echinoidea , Asteroidea, and Ophiu- 
roidea , in which the oral surface looks downwards ( u Eleutherozoci”). 
The three latter classes should not be united under the common name 
Echinozoa. In Echinoids the ambulacra extend from the mouth to the 
calyx (“ zygopodous ”) ; in Asteroids and Ophuiroids the development of 
additional plates causes the ambulacra to be confined to the oral aspect of 
the body (“ azygopodous ”). The term brachiate should not be used, 
since the arms of a Grinoid are formed by addition to the free edge, and 
those of Asteroids and Ophiuroids by intercalation between the radial and 
terminal. The Asteroids and Ophiuroids, . though descended from a 
common “ Stellerid ” ancestor, show very different types of organization. 
A phylogenetic tree is given, p. 211, and a classification of Echinoderms 
proposed ( vide p. 46, Systematic), followed by concise definitions of the 
various groups. 
Camerano describes sexual differences in Strongylocentrotus lividus. 
There are no constant differences in colour. The adult mature males are 
smaller than the females. They differ in shape, the females being 
slightly more flattened. There are no constant differences in the shape 
or arrangement of the skeletal plates or spines. 
Carpenter (1) discusses the following points in the morphology of 
Cystidea. — (1) The body-plates (pp. 1-17) : many Cystids have a caly- 
cular system, which is essentially similar to that of Criuoids. (2) The 
summit openings (pp. 17-32) : the opening in the centre of the ambu- 
lacra is the mouth. The six openings in the summit of Juglandocrinus 
were ambulacral in nature, and food particles entered through them on 
their way to the central mouth, just as they did at the arm-openings of 
the Camerata. The u hydrophores palm6s ” of Barrande are subteg- 
minal ambulacra. The fourth opening of Aristocystis probably 
represented a water-pore, and was excretory in function. The third 
opening, situated in the anal iuterradius (c d), was a genital opening. In 
Oystids, in which no such third opening has been found, the genital ducts 
and rectum may have opened together below the valvular pyramid ; 
just as in the family Pterasteridce the anus and oviducts open into 
a sort of marsupial pouch, and communicate with the exterior by 
the “ oscular orifice ’* of Sladen. In Agelacrinus and Caryocrinus 
the third opening in the interradius (d e) was very probably 
nephridial ; it perhaps represented a madreporite, and also placed 
the water vascular system in communication with the exterior, like the 
fourth opening of Aristocystis and Yolborth’s organ in Glyptosphiera. The 
third opening in the anal interradius of many forms may also have been 
