716 CLASS XII. 
nerve-mass, the par pedale, also connected with the first ganglia by 
two shorter strings, is, in those genera that have no foot, feebly 
developed, or according to GARNER, even absent. The nerve- 
ganglia are usually distinguished by a red or orange colour’. The 
nervous system of the Brachiopoda is not yet perfectly known, but 
seems to be formed after a different typus?. 
Amongst the parts which may be regarded as the seats of senses, 
the conical cérr? are first to be noticed, which are present sometimes 
along the entire margin of the mantle of the Lamellibranchiata, or on 
some parts of the mantle, at the opening of the s/phon for example, 
and which in the Brachiopoda are changed for long, stiff, glistering 
hairs. The mouth, moreover, in the Lamellibranchiata is surrounded 
by two pairs of transversely striped organs of touch of considerable 
size, triangular, elongated or oval laminz, which some consider to 
be accessory gills, from their external resemblance to these organs. 
In the Brachiopoda there are two long arms, beset pectinately with 
filaments like a fringe, situated at the side of the mouth, where 
they are rolled up in a spiral form, and concealed within the shell. 
Organs of vision have, of late years, been shewn by microscopic 
investigation to be present in Pecten, Spondylus, and many other 
genera amongst the Lamellibranchiata, as green, red-yellow, or 
brown tubers, shining brightly, and often set upon a small pedicle 
at the margin of the mantle. In different species more than a hun- 
dred such eyes have been counted*. 
1 Compare R. Garner On the nervous system of Molluscous Animals, Trans. of Linn. 
Soc. XVII. 1835, pp. 485—488, Pl. 24; BuancHarD Observations sur le Systéme nerveux 
des Mollusques lamellibranches, Ann. des Sc. nat., 3ieme Série, 111. 1845, pp. 32I—340, 
Pl. 12, Here may be found a copious historical review of this subject. The two small 
nerve-ganglia that lie near the oval ganglia in Ostrea (BRANDT and RaTZEBURG Medizin, 
Zool. I. 8. 340, 341), BLANCHARD regards as answering to the par pedale (here want- 
ing according to GARNER). Nervous branches that arise from the lateral commissural 
string of the first and hindmost pair, on which in some species (Solen, Arca) even gan- 
gliform swellings are observed, correspond, so it appears, to the sympathetic nervous 
system of articulate animals, especially to the lateral portions of it in the crays, which 
in like manner arise from the collar round the neck (see above, p. 618). Those lamelli- 
branchiates, which are provided with a tubular prolongation of the mantle, have often 
between the muscles, that retract the tube, small nerve-ganglia in addition. 
2 Cuvier Mém. sur la Lingule, p. 8, speaks very indecisively on this point; OWEN 
describes a nerve-ganglion between the basal pieces of the two arms, and two others at 
the side of the mouth. Trans. of Zool. Soc. 1. p. 156. [On the nervous system of Tere- 
bratula see OWEN Introduct, &e. pp. 11, 12 (cited above, p. 710).] 
3 Pout spoke of such eyes smaragdino colore coruscantes, which are situated on the 
larger cirri of the border of the mantle in Spondylus (11. p. 107) and Pecten Jacobeus 
