ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
747 
more delicate and probably of mesenchymatous origin ; these two layers 
are separated from one another by a very delicato connective layer. In 
all groups the ambulacra or tentacles are provided with ganglionated 
nerves ; ganglia are massed round the spines ; in Synapta inhserens the 
peripheral plexus of the skin contains a number of small ganglia, which 
are in relation with groups of glandular cells, which probably produce 
a defensive secretion. M. Cuenot is of opinion that the spheridia are 
certainly sensory organs, and not altered spines ; like the otocysts, they 
are, he thinks, organs of the sense of orientation. 
The organs of reserve have, in very many cases, the form of amoe- 
bocytes of the fluid of the coelom which are filled with fat or albumi- 
noids ; thus loaded they pass into the tissues by diapedesis, and remain 
there till needed. The saccules of Antedon rosacea are probably organs 
of reserve ; they contain a certain number of cells which are filled with 
yellow spherules of a proteid nature. 
The cavities of an Echinoderm body are very complex, for there are 
(1) the coelom, formed by the fusion of the enterocoelic vesicles and 
more or less subdivided in the adult by secondary septa ; (2) the axial 
sinus of Asteroids, Ophiuroids, and Echinoids, which contain the ovoid 
gland, which has an enterocoelic vesicle that has remained isolated ; as 
dependencies of this are the sinuses connected with the genital organs ; 
(3) the ambulacral apparatus (hydrocoel), which is derived from a 
portion of the enterocoel ; (4) the schizocoelic cavities subjacent to the 
nerve-ring and radial cords, which often communicate with the axial 
sinus and with the coelom ; (5) the various lacunar schizocoels, which 
are formed independently in the different groups ; and (6) the supra- 
neural sinuses which represent an invagination cavity. The author 
describes some of these in detail. 
The three types of hermaphrodite Echinoderms have each a special 
form of hermaphroditism ; Asterina gibbosa is male when young, and, 
later on, exclusively female. In Synapta, at each epoch of maturity, the 
animal first ejects eggs only, and, later on, becomes exclusively male. 
What is remarkable in this case is that all the individuals of one locality 
are in the same stage, whence we must conclude that the ova are not 
fertilized till some time after expulsion. In Amphiura squamata the 
testes and ovaries are separated, the former being radial and the latter 
interradial in position; cross-fertilization is most frequent probably, 
but self-fertilization is possible. In Ophiactis virens the gonads are not 
developed till very late, and after the animal has already reproduced 
itself several times by median division. 
The author is unable to accept any of the published phylogenies of 
this great group. The simplest type he can imagine is a Prosynapta , 
from which the Synaptidae of the present have been evolved ; Prosynapta 
gave rise to a Proliolothuria, whence the Holothurida and Elasipoda have 
been derived. Proliolothuria became Procystus , which gave rise to 
Cystoids, Blastoids, and Crinoids ; it was at this time that the calcareous 
plates found a continuous skeleton, and that the larval anus was 
obliterated to open again independently in spots varying with varying 
types. Procystus was the parent of Proechinus , ancestor of all the 
Echinids, and the ancestor of Proaster, whence diverged the Asteroids 
and Ophiuroids. The author recommends this theory as conciliating the 
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