26 SUPPLEMENTARY APPENDIX. 



In Rh. nigricans the alimentary canal terminates exactly as in Waldheimia, and not as described by 

 Mr. Huxley in R. psittacea. (See Introduction, p. 94, and 'Woodward's Manual,' p. 226.) 



Mr. Huxley again states: "If the extremity of the intestine, either in Rhynchonella {psittacea), or 

 Waldheimia (Jlavescens), be cut off and transferred to a glass plate, it may readily be examined microscopically 

 with high powers, and it is then easily observable that its fibrous investment is a completely shut sac. In 

 Rhynchonella (psittacea), the enlarged caecum is often full of diatomaceous shells, which it is impossible to 

 force out at its end, while if any aperture existed they would of course be readily extruded. 1 



" However, anomalous, physiologically, then, this caecal termination of the intestine in a molluscous 

 genus may be, I see no way of escaping from the conclusion that in the Terebratulidce (at any rate in these 

 two species) it really obtains. There are other peculiarities about the arrangement of the alimentary canal, 

 however, of which I can find either no account or a very imperfect notice. 



"The intestinal canal has an inner, epithelial, and an outer fibrous coat ; the latter expands in the middle 

 line into a sort of mesentery, which extends from the anterior face of the intestine, between the adductors, 

 to the anterior wall of the visceral chamber, and from the upper face of the intestine to the roof of the 

 visceral chamber ; while posteriorly it extends beyond the intestine as a more or less extensive free edge. 

 I will call this the mesentery. 



"From each side of the intestinal canal again the fibrous coat gives off two 'bands,' an upper which 

 stretches from the parietes of the stomach to the upper part of the walls of the visceral chamber, forming a 

 sort of little sheath for the base of the posterior division of the adductor muscle, which we will call the 

 g astro-parietal band ; and a lower, which passes from the middle of the intestine to the parietes, supporting 

 the so-called ' auricle.' I will call this the ilio-parietal band. 



"The ilio-parietal andgastro-parietal bands are united by certain other ridges upon the fibrous coat of the 

 intestine, from the point of union of which in the middle line of the stomach posteriorly, a pyriform vesicle 

 depends. The mesentery divides the liver into two lateral lobes, while the gastro-parietal band gives rise to the 

 appearance that these are again 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 be con- 

 founded with an arterial ramification of the liver. This description applies more especially to Rhynchonella 

 {psittacea) and Waldheimia {Jlavescens), but the arrangement in Lingula is not essentially different." 



Mr. Huxley enters into many important details connected with the circulatory system of Terebratula 

 Jlavescens, 2 Rhynchonella psittacea, and Lingula anatina, and especially on the organs, " one on each side 

 of the body which have been recognized 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 distributed into that glandular mass which Cuvier called ovary, but which is now known to be 

 the genital gland of either sex. 



" In 1845, however, M.Vogt's elaborate memoir on Lingula 3 appeared, in which the true complex structure 



1 Mr. Woodward states that he forced the contents of the canal through its termination, with the 

 forceps. 



2 It is only just to observe that Mr. Huxley has only examined Waldheimia Jlavescens, which he places 

 in opposition with those of Terebratella chilensis, on which Professor Owen's views were founded, but which 

 he has not examined, so that at present the examinations not being made on the same animals cannot finally 

 invalidate the statements of Professor Owen. 



3 Neue Denkschriften der Schweizerischen Gesellschaft fur die gesammte Wissenschaften ; or, 

 'Nouveau Memoirs de la Soc. Helvetique,' vol. vii, p. 1, 1845. I may also state, that Cuvier's first paper 

 on the animal oj Lingula, was published in the ' Bulletin de la Soc. Philomatique of Paris,' vol. i, p. iii, 

 PI. 7, 1797. He there states: "II parait que ce genre (Lingula) dans lequel on connait deja. trois especes, 

 reuni avec les Tei'ebratules, la Fissurelle de Bruguiere et le Patella anomala de Linneus peut former une 

 famille assez naturelle dans l'ordre des Acephales." 



