1873.] 345 [Morse. 
arteries to be nerve cords, and traced them to their posterior gang- 
lionic enlargements. 
Respiratory Apparatus. 
The pallial membrane in the Brachiopoda sustains the principal 
respiratory apparatus. It is in this membrane that the larger vessels 
oceur, and as I shall show in my memoir on Lingula, the pallial 
membrane is divided into oblique transverse sinuses, which run par- 
allel to each other. From these arise numerous flattened ampulla, 
which are highly contractile. 
The circulating fluid courses in regular order up and down these 
sinuses, entering each of the ampulle in turn. 
Voct and Owen were quite right in their determinations of these 
organs. ‘They represent the branchie of Lingula; but from the con- 
tractile nature of the ampulle, and their almost certain contraction 
in alcohol, they have escaped the notice of others who have studied 
specimens in which the ampullee were inconspicuous. 
Thus Hancock was unable to find them in the two species of Lin- 
gula, studied by him, and says, “ The bladder-shaped enlargements 
of the lateral pallial sinuses, alluded to by Dr. Vogt, are nothing more 
than swellings occasioned by the contraction of the pallial, or mar- 
ginal fold, which, pressing upon the extremities of the sinuses, throw 
their walls into wrinkles, and hence their peculiar appearance.” } 
These ampulle are very conspicuous in living Lingule. On one 
side of the dorsal pallial membrane in an ordinary specimen there are 
twelve sinuses, having in the aggregate eighty-five ampulle, number- 
ing from five to eleven in each sinus. In life they form very interest- 
ing objects. They project, or hang from the walls of the pallial 
membrane, like teats. Their walls are perfectly transparent, and 
the circulating fluid can be seen rapidly coursing into, and out of each 
one in turn. 
The following figure (Fig. 19) shows Fig. 19. 
a row of five ampulle drawn from life, 
within which the blood corpuscles can BOG: (\ 
be seen circulating. arn 
Claparéde says that in the normal % 
branchia of an Annelid there cannot 
be any mixture of arterial and venous blood. The artery trav- 
elling as far as the end of the branchia, where it returns as a 
1 Hancock, Trans. Royal Soc. Vol. cXLvVIII, p. 852. 
