4 Ech. 
ECHJNODERMATA. 
plexus of the Echinozoa may not be glandular in nature ; he regards as 
well established the existence of radial blood-vessels in Ophiurids. He 
thinks that Ludwig has demonstrated the existence in Amphiurci of the 
representatives of the under-basals of Crinoids, and that the dorsal side 
corresponds to the dorsal, and not, as Ludwig thinks, to the ventral side 
of a Orinoid. 
Ludwig (28) has some very important observations on development, 
which he thinks must be looked upon as metamorphic in character, 
though he is far from supporting the well-known theories of Haeckel. 
He regards the various forms of larvae as being secondary, and modified. 
Intermediate larval stages may be interpolated, but do not affect the 
essential characters of development, being adaptations proper to the 
larval life, and disappearing with its cessation. The dorsal pore in the 
embryo appears to have primitively led into the enteroccel, and its 
connection -with the hydrocoel, therefrom developed, is only a secondary 
phenomenon ; the earlier relation is retained by the Crinoidea. Atten- 
tion is directed to the “ larval orgaus,” and a study of the development of 
the skeleton results in demonstrating its resemblance to what obtains 
in the Ophiuroidea. No definite plane of symmetry is to be detected in 
the adult, and if any interradius can be spoken of as the “ anterior ” 
one, it is that in which we find the remnant of the larval organ and 
the anus; when these are lost it may still be recognized by having, 
in a dorsal view, the madreporite to the left of it. The ambulacral 
plates of Echinoids are regarded as the homologues of the adambu- 
lacral plates of the Asterid and the lateral plates of the arms of the 
Ophiurid. The so-called odoutophore is now (in opposition to an earlier 
view) regarded as an unpaired interambulacral plate. 
Perrier (36) regards Caulaster as an Asterid of especial significance, as 
it is provided with a dorsal peduncle, which he looks upon as indicating 
its relations to the stalked forms ; the nearest ally among known genera 
is thought to be Ctenodiscus , which has a slight dorsal tubercle. 
Perrier (35) has examined sixteen discs and other remnants of a 
species of Brisinga, of which anew species, B. edwarsii, has been dredged 
in the Atlantic ; he regards B. coronata and B. endecacnemos as two forms 
of the same species, and he points out that the dorsal skeleton is not 
developed in young forms, and in the adult is only found where the 
genital glands are developed. The form appears to indicate some close 
relation between the Aster oidea and the Ophiuroidea , while the early 
arrangement of the plates of the disc recalls the constitution of a 
Crinoid. 
Apostolides (2) has made an elaborate investigation into the structure 
of the Ophiuroidea , devoting himself largely to the study of living speci- 
mens, and he reports on the development of Ophiothrix versicolor and 
Amphiura squamata. 
Koehler (25) finds that cross fertilization is possible, within very wide 
limits, among the species of the Echinoidea, but while the ova of one 
species may be fertilized by the spermatozoa of another, the reverse may 
not hold good. Regular breed better with other regular than with 
irregular Echinoids. 
