166 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



carl innate, ferric phosphate, and magnesium ammonium phosphate. The excretion contains no 

 uric acid. 



The amount of the excreted products in the renal sac may be quite considerable. In one 

 rase the deposit obtained from the four sacs amounted to 3.28 grams. 



The secretion of the pericardial glands is often quite large in amount, being sufficient to glue 

 the viscera together and cause considerable trouble to the dissector. Of course there is a proba- 

 bility that the glands have been stimulated to abnormal activity by the handling of the animal. 

 The coagulated secretion appears much like mucus. Kefekstein found no traces of uric acid 

 in either the pericardial glands or their secretion. 



BODY CAVITY. 



The body cavity of Nautilus is very extensive, and consists of two distinctly separated 

 portions — an anterior hsenioeoel and a posterior and ventral ccelom. The principal portion of 

 the hajmociel forms a space around the oesophagus with its crop-like distensible portion, and the 

 liver, occupying the entire space between these organs and the body wall. (Fig. 7.) The haHuocoel 

 is continued anteriorly in the form of many splits and spaces between the muscles and membranes 

 around the buccal mass. These cavities and others which communicate with the main portion of 

 the hsemoccel are in free communication with blood sinuses in the various organs. 



The ha?ruoccel is traversed by many fine shreds of connective tissue, which pass from one to 

 another portion of the body wall or from the walls of the body to the viscera lying within the 

 cavity. All these connections are exceedingly delicate, and are so easily ruptured or dissected 

 that for all purposes of dissection the organs in the ha?mocoel lie freely in the cavity. The vena 

 cava lies along the ventral wall of the body and through its dorsal wall are numerous openings, 

 from twenty to seventy-five, allowing free passage to the blood from the hsemoccel into the vena 

 cava. At least, as the blood in the vena cava moves toward the gills and through them to the 

 heart, it is more justifiable to presume that the blood which enters the hsemoccel through numer- 

 ous sinuses is drawn into the vena cava than that the flow occurs in the opposite direction. 

 Some of the. openings in the walls of the vena cava are large enough to admit the end of a probe 

 1 millimeter or more in diameter; others are so small as to be scarcely visible. 



The ccelom is situated posteriorly to the hsemoccel, and is completely separated from it by 

 a thin membranous wall. (Fig. 7.) This wall, which I have called the ha?mocoelie membrane, 

 is attached to the body wall dorsally along the line of the dorsal aponeurotic band. (Fig. 7, X.) 

 At the sides of the body its edges are fastened to the inner surfaces of the shell muscles, passing 

 downward and slightly backward. The ventral edge is attached to the ventral body wall along 

 the line of junction of the body wall and the inner wall of the mantle fold. 



The anterior face of the hasmoccelic membrane is rough, and is attached to the organs within 

 the hsemoccel by a few strands of connective tissue. The posterior, ccelomic face of the mem- 

 brane is smooth and covered by the ccelomic epithelium. 



The attachments of the ha?moc<elic membrane to the bod}' walls are considerably in front of 

 the posterior ends of the organs contained within the hffimoccel. Consequently it is pushed 

 backward by the lobes of the liver, forming sack-like coverings for these. (Fig. 7, L, L.) It 

 covers other organs in a manner to be described presently. 



There is a considerable mechanical advantage in the dorsal attachment of the membrane, on 

 account of the membrane forming sac-like coverings for the backwardly projecting viscera; it 

 also serves to support these viscera. The support is rendered much more effectual by the attach- 

 ment of the membrane to the body wall along the dorsal aponeurotic band, where the latter is 

 itself attached to and supported by the shell, than it could be if the membrane were attached to 

 the loose wall of the body back of the aponeurotic band. 



The ccelom also is a cavity of very considerable extent. It occupies the entire posterior 

 portion of the body, extending forward dorsally above the lobes of the liver and ventrally into 

 the mantle fold. (Figs. 7 and 36.) 



