166 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



cnrboimtc, ferrif phosphate, and imigno.sium auimoniuin phosphate. The excietion eontaiiis no 

 uric aeid. 



The amo'int of the excreted products in the renal .sac ma.y he (juite considerable. In one 

 ca,sc the deposit obtained from tiie four .sacs amounted to 3,;i8 j^rams. 



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

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

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

 The coagulated secretion appears nuich 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 hsemoccel and a posterior and ventral coelom. The principal portion of 

 the ha?moc(el forms a space around the (esophagus with its crop-like distensible portion, and the 

 liver, occupying the entire space lietween these organs and the body wall. (Fig. 7.) The hiemoc(el 

 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 conununicate with the main portion of 

 the h{emoco?l are in free communication with blood sinuses in the various organs. 



The hamiocosl is traversed by many line shreds of connective tissue, which pass from one to 

 another portion of the liody wall or from the walls of the body to the viscera lying witliin 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 hsemocoel lie freely in the cavity. The vena 

 cava lies along the ventral wall of the l)ody and through its dorsal wall are luuuerous t)penings, 

 from twenty to seventy -tiv(\ allowing free passage to the blood from the hiemoccel 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 hiemoc(fl 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 cadom is situated posteriorly to the hiemoc(jel, and is completely separated from it t)y 

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

 is attached to the body wall doi'sally along the line of the dorsal aponeurotic liand. (Fig. 7, X.) 

 At the sides of the body its edges arc 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 hiemoccelic membrane is rough, and is attached to the organs within 

 the hiemoc(el by a few strands of connective tissue. The posterior, coelomic face of the mem- 

 brane is smooth and covered by the ccelomic epithelium. 



The attachments of the hamiocuelic membrane to the ))ody walls ai'c considerably in front of 

 the posterior ends of the organs contained within the hremocoel. Con.sequently it is pushed 

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

 covers other organs in a manner to l)e described presently. 



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

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

 also serves to support these viscera. The support is n-ndered nuich more eflectual by the attach- 

 ment of the membrane to the body wall along the dor.sal 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 coelom 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 ventraily into 

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



