470 



pared to the atrium of the Ascidianida, and the water-chambers of 

 the Cephalopoda and other mollusca. The pseudo-hearts enable the 

 perivisceral cavity to communicate with the exterior, and convey 

 away the genital, and probably the renal products. On this head 

 the author says : 



"From the foregoing account of the circulatory apparatus, it 

 would appear that the perivisceral chamber, and its various so-called 

 vascular ramifications in the mantle, are not connected with the 

 blood-system. This is no doubt a startling fact. I commenced the 

 present investigation fully imbued with the opinion that these parts 

 were blood reservoirs and channels, and I only relinquished it when 

 it became no longer tenable. Step by step the points relied on had 

 to be abandoned, until at length the full conviction was arrived at 

 that I had been seeking to establish a fallacy. I have been unable 

 to discover any communication between the true blood-system and 

 the pseudo-vascular ramifications in the mantle or the perivisceral 

 chamber. Injections were thrown into this chamber, but none of 

 the fluid found its way into any part of the lacunary system. The 

 pallial lobes were removed, and the great pallial sinuses distended to 

 their fullest capacity, with exactly the same result ; and it was not 

 until the tissues were ruptured on applying great pressure, that 

 a little of the injected matter was extravasated into the peripheral 

 lacunes. The perivisceral chamber, then, and all its various ramifi- 

 cations, are in no way connected with the true blood-system." 



The nervous system of the articulated Brachiopoda is described at 

 length. Besides the principal suboesophageal ganglion, two minute 

 enlargements are shown to exist upon the anterior part of the oeso- 

 phageal commissure, and two small pyriform ganglia are described 

 in connexion with the under part of the principal ganglion. The 

 peripheral nerves are minutely traced out, and two peduncular 

 nerves, not hitherto known to exist, are described. The author 

 denies the existence of the so-called " circumpallial " nerves. He has 

 been unable to detect the nervous centres in Lingula, and he is in- 

 clined to regard the cords, described as nerves in that genus by Prof. 

 Owen, as blood- sinuses. 



The author next makes some remarks on the structure of the 

 shell, pointing out that in Terebratulina caput-serpentis there are 

 two distinct layers, an external and an internal ; and he then draws 



