4 Brach. 
BRACHIOPODA. 
of cells derived from the outer layer of the mantle. This last consists of 
a cartilaginous lamella covered with cells on either side and containing 
the reproductive organs in its folds. It serves also as an organ of reproduc- 
tion. The arms aro formed of cartilaginous material, and are penetrated 
by two canals, one of which sends branches to the cirri ; the canals also form 
a plexus round the oesophagus and communicate by two small openings 
with the coelom. There are eleven muscles, the most important being 
the adductors and protractors and those which fix the arms. The anus is 
in the middle line of the body, and slightly dorsal ; the alimentary canal 
is ciliated internally ; the liver is simply cellular, and has a delicate 
sheath of cartilaginous tissue, wanting in Discina and Lingula. Proper 
circulatory and respiratory organs are absent. The sexes are separate ; 
the ovaries are modified coelomic epithelium with a connective tissue 
plexus. There is an oesophageal nerve-collar, from the dorsal swelling 
of which the brachial nerves proceed, the mantle, viscera, and muscles 
being supplied by the sub-oesophageal portion. The general relations of 
the group are discussed ; Joubin. 
The shell of Lingula pyramidata consists of horny and calcareous 
layers alternately ; a cuticle is continued over the whole surface of the 
shells and the peduncle, below which, as also in other parts of the shell, 
are clusters of small homogeneous corpuscles, probably homologous with 
those in the vortical septa of the Testicar dines. The horny layers aro 
produced into the peduncle as a “ supporting lamella.” The cuticle is 
probably a modified larval integument, and the shell contains in all parts 
processes of the coelom. The body -wall, mantle, and peduncle all’ consist 
of epithelium, both ectodermal and peritoneal, and supporting tissue. 
The character of the ectoderm varies in different parts of the body, 
being furnished in certain regions with oval structures like taste-bulbs. 
Immediately below the ectoderm is a supporting substance, the central 
nervous system intervening in certain places ; where this is the case 
spindle-shaped nucleated cells occur. The supporting tissue also contains 
certain calcareous plates comparable with those found in the Testicardines. 
In the peduncle the supporting lamella becomes a net-work enclosing 
bundles of spermatozoa. Many structures previously regarded as mus- 
cular have no claim to this designation. No pulsating organ was found ; 
four kinds of corpuscles found in the coelomic fluid are described. The 
interior of the alimentary, canal, is ciliated, and from the stomach hepatic 
caeca are given off. The nervous system recalls that of Waldheimia ; 
there are five ganglia — one sub-oesophageal, two ventro lateral, and two 
supra-cesophageal — which are united by connectives and commissures. 
The cord between the ventro-lateral and supra oesophageal ganglia gives 
off pallial nerves and passes along the base of the arms, which are them- 
selves supplied by the supra-oesophageal ganglia. The existence of 
Schulgin’s sensory cells is doubtful. Lingula is hermaphrodite, but the 
two kinds of sexual elements are not developed at the same time. The 
genital products are derived from the coelomic epithelium in the mantle ; 
in the visceral chambers the ovaries occupy the mesenteric bands, the 
spermatozoa the peripheral walls. The segmental organ appears to act 
as sperm-duct as well as oviduct ; Beyer. 
