BRACHIOPODA 175 
developed in the mantle and in those parts of the body-wall 
next to the shell, and send off numerous caecal processes into 
the canals permeating the substance of the latter. The blood is 
probably aerated as it comes through the vessels of the mantle. 
The presence of a central heart in Argiope is a matter of dis- 
pute if it exists, it is a contractile vesicle situated dorsal to 
the stomach; a spherical vesicle is found in this position in 
Waldheimia, but its relation to the blood-vessels is not very 
definitely known. 
The nephridia, which also function as genital ducts, open 
internally, with large funnel-shaped mouths, which are directed 
towards the posterior end of the dorsal shell. These openings 
lead to short tubes which run in that part of the body-wall 
which is pushed in to form the brood pouch; into this they 
Fre, 112.—The posterior quarter of a Waldheimia australis has been removed, in 
order to show the relations of alimentary canal, nephridia, etc. The coelom is 
represented black. From a dissection by J. J. Lister. 
1. Dorsal shell. 7. Intestine. 
2. Ventral shell. 8. Tendons of adductor muscles. 
3. Stomach. 9. Ovary. 
4, Liver. 10, Internal funnel-shaped opening of 
5. Gastroparietal bands. nephridia with three ova drop- 
6. Heart. ping in. 
eventually open. The walls of the tube consist of a connect- 
ive tissue basement membrane lined by glandular cells 
crowded with brown concretions. Some of these cells are 
also ciliated. 
