DESCRIPTION OF PLATES. 823 



Fig. 7. Dissection of the pericardium from below to show the three fontanelles in the 

 pallio-visceral ligament leading from the pericardium to the perivisceral coelom. [Reduced 

 from Quart. J. Micr. So., Vol. xl. 1897, PL II. fig. 2.] 



p.l. Pericardial ligaments. 



p.g. Pericardial glands. 



b.c. Branchio-cardiac vessels. 



a.p.a. Anterior pallial artery. 



py. Pyriform gland. 



g.d. Genital duct. 



r.s. Outer renal sac (cf. PL LXXV.). 



The pyriform body and its ligament form part of the outer border of the middle 

 fontanelle and here somewhat encroach upon it so as to disguise its full extent. The 

 posterior pallial artery is seen crossing the ventral surface of the heart, disappearing behind 

 the pyriform ligament through the middle fontanelle. The heart is bound to the pallio- 

 visceral ligament (which constitutes the fundus of the pericardium) by the cardiac ligament. 



Fig. 8. Dissection of the branchial apparatus of the right side. The membranous portion 

 of the mantle has been turned back and partly removed. The efferent trunk (b.c. 2 ) of the 

 larger gill has been cut across and the gill itself turned partly round to present the afferent 

 surface which has been laid open to expose the cavity of the reno-branchial vessel (r.b.~). 

 The portion of the latter which lies within the pericardium is left intact. 



c.e. Cut edge of the mantle at the junction of its membranous and visceral portions. 



r.s. and p.g. Renal sac . and pericardial gland of the macrobranchiate segment. 



b.c? Extra-pericardial and intra-pericardial portions of the branchio-cardiac trunk. 



b.c' Branchio-cardiac vessel of the lesser gill (seen lying across in front of the greater gill). 



v. Heart. 



pi.v.l. Pallio-visceral ligament. 



p.l. Pericardial ligaments. 



a. Position of annulus. 



s. Position of septal aponeurosis. 



m. Mantle. 



Fig. 9. Portion of body behind the funnel to show veins entering the vena cava. 



f.o. Funnel-organ. 



I. Limbus or ligament passing from f.o. over the surface of the shell-muscles. 



Fig. 10. Ventral view of the pallio-visceral region of N. pompilius, to show the paired 

 pallial veins as displayed by automatic injection with air or gas after removal of the animal 

 from the shell. The finest ramifications of the veins throughout the substance of the 

 membranous portion of the mantle are thus revealed, but only the main branches are shown 

 in the drawing. 



PLATE LXXXIII. 



Figg. 1 and 1 a. Amoebocytes , (blood-corpuscles) of JV. macromphalus. They undergo 

 relatively rapid amoeboid changes of form ; some contain fine granules, but most of them are 

 laden with coarse, bluish, refringent granules which dissolve away in acetic acid leaving a 

 spongy plasmatic reticulum. The cells vary in size and tend to accumulate in masses on 

 the slide, sometimes appearing to form plasmodia (fig. 1 a). When killed and stained with 



