,8,,. OBSERVATIONS ON THE BRACHIOPODA. 605 



true arteries. Dr. Joubin considers them to be lymphatic channels 

 (lacunes) with a speciahsed function. 



The digestive canal of W. veiwsa differs apparently but little 

 from that of other articulated Brachiopoda. The general dimensions 

 are described as larger, and the constituent parts as more clearly de- 

 fined than in the smaller species. The mouth is formed by a shallow- 

 ing of the digestive tube, ultimately terminating in an orifice within 

 the brachial groove. The stomach is a large, deep pocket, with thick 

 side walls. He notes the occurrence of a papillary prominence of the 

 digestive epithelium, situated just beneath the vessel elTerent from the 

 heart, which may possibly serve as an organ of taste, but does not 

 absolutely affirm that it is one. The so-called " liver " in this species 

 is described as remarkably developed. It is the largest organ and 

 attains relatively an enormous size. There are two hepatic canals in 

 each lobe, the anterior is the larger. The cells present well-marked 

 characters. Some are mucus cells, others granular. He considers 

 that these two kinds of cells secrete distinct digestive ferments and 

 that mucus is secreted by the calciform cells. As the hepatic fluid 

 yields none of the elementary characteristics of bile, as understood 

 among the superior organisms, and contains distinctive products not 

 found at all in the biliary fluid. Dr. Joubin would change the name 

 of this secreting organ into that of " stomacal gland," maintaining 

 that the so-called "liver" of the Brachiopoda presents none of the 

 features characteristic of that structure in other animals. 



The organs described as "accessory hearts" by Hancock were not 

 found to be present in any of the specimens of Waldheiviia venosa Dr. 

 Joubin examined. He considers them as "accidental vesicles " anoma- 

 lous and inconstant. The occurrence, however, is noted and figures 

 and descriptions are given of structures which he names supplementary 

 hearts. These differ completely both in structure and relations from 

 the "accessory hearts" of Hancock. They cannot be otherwise desig- 

 nated, if the name of " heart " be applied to the principal organ, for 

 their structure is identical, and they perform the same function, that 

 of receiving the lymph originating from the intestine. These supple- 

 mentary hearts are symmetrically situated, the one on the right and 

 the other on the left of the posterior region of the stomach. The 

 organs are in reality oval-shaped blood-channels, larger and more 

 dilated than in general. They are usually filled with white corpuscles. 

 The principal heart receives and the median aorta conveys the 

 lymphatic fluid of all the dorsal region of the stomach, the " supple- 

 mentary hearts" collect that derived from the inferior and lateral 

 regions, the nutrimental fluid passes through all these organs. The 

 first, or principal heart, nourishes the brachial system ; the two 

 latter the genital organs via the two main lateral blood-vessels, which 

 alone are truly vascular. These are composed of an external epithe- 

 lium, a central layer of amorphous tissue, and an internal epithelium 

 most distinctly characterised. 



