24 
on the theory of unity of plan, but relates in the Apteryx to the exigences of respiration 
with fixed lungs and large air-cells. 
Renal and Genital Organs. 
The kidneys' of the Apteryx are situated symmetrically, and lodged, as in other birds, 
in the irregular hollows of the back part of the cavity of the pelvis ; their posterior sur- 
face presents corresponding projections ; the anterior surface is smooth and almost flat : 
the mesial edges of the kidneys are nearly straight and parallel, and very close to each 
other, but do not coalesce at any part ; the outer edges are notched. Each kidney mea- 
sures 3 inches in length, 11 lines across the broadest part, which is one-fourth from the 
anterior extremity, and 4 lines at the thickest part. It is divided into five lobes by ob- 
lique fissures, extending into the posterior surface of the gland: the middle lobe is the 
largest. These lobes appear to have a compact and even surface, but their cerebriform 
convolutions can be readily unravelled. The weight of both kidneys is 2 drs. 36 grs. 
avoirdupoise. The tortuous ureter (w, Pl. 1V.) emerges from the inner side of the posterior 
extremity of the kidney, and after a course of an inch and a half, terminates, as above 
described, in the upper and back part of the uro-genital cavity. 
The supra-renal bodies (a, «, Pl. IV.) were of an oval form, and yellow colour ; of a 
homogeneous texture ; each 3 lines in length, and adhering closely to the vena cava (u). 
The male organs of generation consist of two pretty equally developed testes (y, y, 
Pl. IV.) situated on the sternal aspect of the atlantal extremities of the kidneys, and on 
each side of the crura of the diaphragm. They were of a subcompressed oval figure, 
with a somewhat angular external margin, about 1 inch in length and 8 lines in breadth 
in the largest male Apteryx ; but the dimensions of these glands are of course liable to 
vary according to the season or state of sexual excitement. Thus in the younger male 
Apteryx they were subcompressed, subtriangular bodies, imbedded in the sternal and 
lateral aspects of the supra-renal bodies, and not exceeding 5 lines in length. The vasa 
deferentia (2, z, Pl. IV.) are formed by the union of numerous most minute efferent tu- 
bules, which pass from the testes, without forming an epididymis, into a soft amorphous 
substance, of a gray colour, which lies between the testes and the bright yellow supra- 
renal body. Some of the efferent tubules are lost in the gray substance, which seems to 
be the remnant of the corpus Wolfianum ; but the greater part perforate that body, and 
proceed to form the vas deferens. This tube is continued in the usual transversely 
undulated course, along the sternal aspect of the kidneys, and towards their mesial mar- 
gins, to the urethro-sexual compartment, and terminate each on a prominent papilla 
(h, h, Pl. IV.), situated in the uro-genital cavity, four lines below, and to the outer side 
of the urethral outlets, and three lines above the sides of the crescentic fold which sep 
. a- 
rates the uro-genital from the vestibular compartment of the cloaca. 
The cresses or 
1 Pl. IV. v, v, 

