418 SURGEON J. C. THOMPSON ON THE 



dividing one lung fi-om the other. There are two perforations 

 afibrding communication between the lungs ; the larger, measuring 

 2 mm. in diameter, is at the termination of the trachea, and the 

 smaller, measuring 1 mm. in diameter, is near the posterior 

 border of the septuin. The trachea ends abruptly 3 mm. behind 

 the apex of the heart, and on the lower surface of the bridge. 



The right lung extends from the 49th to the 119th gastrostege. 

 Anteriorly, it reaches 8 mm. beyond the border of the bridge ; 

 it is adherent to the right side of the trachea for the distance of 

 6 mm., and has a free apex 2 mm. long. The trachea communi- 

 cates with the lung 2'5 mm. behind the point where they join. 



The left lung extends fi-om the 50th to the 77th gastrostege. 

 Anteriorly it terminates in an acutely pointed free apex 8 mm. 

 long, at the level of the auriculo-ventricular septum. Poste- 

 riorly the lung terminates in a blunt cone, and towards the 

 end the walls are a trifle thinner and the alveoli larger. There 

 are two pulmonary veins. The right courses along the angular 

 ventral border of the right lung and enters the anterior inferior 

 corner of the auricle. The left commences at the posterior 

 border of the bridge and enters the posterior inferior corner of 

 the auricle. This vein is the thicker of the two. It is formed 

 of two branches that arise along the mesial side of each lung ; 

 the branch from the right lung is the larger, and it has frequent 

 anastomoses with the right pulmonary vein. 



The liver extends from the 64th to the 116th gastrostege. 

 There is no trace of segmentation. 



The centre of the gall-bladder is at the 129th gastrostege. 



The right kidney extends from the 146th to the 155th, and 

 the left from the 150th to the 161st gastrostege. Each is 

 semidivided into nine irregular lobes. The right kidnej' is 

 supplied by two renal arteries, the anterior entering at the 

 second and the posterior at the sixth lobe. There is a single 

 renal vein leaving the anterior tip of the organ, and this promptly 

 unites with its fellow to form a common trunk. 



The lining of the rectum is smooth. The ileo-csecal valve is 

 at the 157th gastrostege. The rectal caecum is 9 mm. long, and 

 is directed forwards and lies on the right side of the ileum. Its 

 walls are thin, and the opening into the csecum is just anterior 

 and to the right of the valve. Its lumen was fdled with fsecal 

 matter, though the caecum and rectum were empty. 



Along the dorsal wall of the cloaca there is a longitudinal, 

 rounded ridge, which terminates in a papilla 1 mm. in length, 

 and at the level of the posterior border of the last gastrostege. 

 This ridge is formed by the two parallel tubes of the completely 

 divided vagina ; these terminate in two separate orifices at the 

 tip of the papilla. The lining of the vagina is finely and 

 longitudinally plicate. According to Cope * the vagina in the 

 Peropoda is undivided and the walls are nearly or quite smooth, 



* Op. cit. p. 7Q0. 



