CONTRIBUTIONS TO THE ANATOMY OF THE BRACHIOPODA 329 



Other ridges upon the fibrous coat of the intestine, from whose point 

 of union in the middle Hne of the stomach posteriorly, a pyriform 

 vesicle {n) depends. 



The mesentery divides the liver into two lateral lobes, while the 

 gastro-parietal bands give rise to the appearance that these are agaim 

 divided into two lobules, one above the other. I am inclined to think 

 that these bands are what have been described as ' hepatic arteries,' 

 at least there is nothing else that could possibly be confounded with 

 an arterial ramification upon the liver. 



This description applies more especially to Rhynchonella and Wald- 

 heimia, but the arrangement in Lingjila is not essentially different. 



2. The Circulatory System of Terebratitlida. — Considerable differ- 

 ences of opinion have prevailed among comparative anatomists as tO' 

 the nature and arrangement of the vascular system in the Brachio- 

 poda. A pair of organs, one on each side of the body, have been re- 

 cognized as Hearts since the time of Cuvier, who declared these 

 hearts in Lingula to be aortic, receiving the blood from the mantle 

 and pouring it into the body, the principal arterial trunks being dis- 

 tributed into that glandular mass which Cuvier called ovary, but 

 which is now known to be the genital gland of either sex. 



Professor Owen in his first memoir follows Cuvier's interpretation,, 

 stating that in Orbicida the pallial veins terminate in the hearts, 

 from which arterial branches proceed to the liver and ovary. Pro- 

 fessor Owen further adds for the Brachiopoda in general, — 



" Each heart, for example, in the Brachiopoda is as simple as in 

 Ascidia, consisting of a single elongated cavity, and not composed of 

 a distinct auricle and ventricle as in the ordinary Bivalves," and he 

 compares the hearts of Brachiopoda to the auricles of Area, &c. 

 (Trans. Zoological Society, vol. i. p. 159)- 



In 1843, however, M. Vogt's elaborate memoir on Lingula ap- 

 peared, in which the true complex structure of the ' heart ' in this 

 genus was first explained and the plaited 'auricle' discriminated 

 from the 'ventricle ;' and in 1845, Professor Owen, having apparently 

 been thus led to re-examine the circulatory organs of Brachiopoda,, 

 published his ' Lettre sur I'appareil de la Circulation chez les Mol- 

 lusques de la Classe des Brachiopodes,' in which he felicitates M. 

 Milne-Edwards on the important confirmation of the views which 

 the latter entertains with respect to the lacunar nature of the circu- 

 lation in the Mollusca, afforded by the Brachiopoda, and describes 

 each heart of the Terebratulidae as consisting of a ventricle and a 

 plaited auricle, the pallial veins not terminating in the latter but in 

 the general visceral cavity. As the Professor does not recall the view 



