SCHULTE, SEI WHALE. 459 



UROGENITAL APPARATUS. 

 (Plate LI, Fig. 1, LI I, Figs. 1, 2.} 



The urinary and reproductive organs of Balcenoptera, apart from descriptions contained 

 in reports of individual specimens, have been the subject of more particular investigation on 

 the part of Beauregard and Boulart, 1 and more recently of Daudt, 2 to whom we owe a most 

 thorough and critical study of these organs in the Cetacea. In most respects conditions in this 

 fcetus closely resemble his descriptions of B. musculus; there are, however, some differences of 

 which the most important is the mode of fixation of the kidneys. 



Kidneys. These organs are adherent to the parietes in the whole extent of their dorsal 

 surfaces, and not suspended from their mesal borders as in the older fcetus of Daudt (length 

 104 cm. cf, cf. his text figs. 4, 5 and 6). On the contrary the peritoneum passes over the kidneys 

 from the mesentery to their lateral margins and thence to the abdominal walls in the manner 

 usual in mammals and as in Eschricht's 3 fcetus of B. rostrata. This seems also to have been 

 the case in Daudt's younger fcetus (length 50 cm.). I could not detect on either side a muscular 

 connection with the diaphragm. The kidneys are slightly asymmetrical, the right lying farther 

 rostrad and overlapping by its upper pole the origin of the diaphragm, while the left just falls 

 short of reaching the diaphragm. The degree of asymmetry in this fcetus is thus very small, 

 but is in the same sense as in Daudt's fcetus and is additional evidence that the greater bulk 

 of the liver on the left is not the determining factor in the position of the kidneys, when as so 

 generally happens in mammals the right is slightly lower than the left. In addition to the peri- 

 toneum which covers their ventral surfaces the kidneys are invested by a thick and strong fascia 

 renalis, which in this preserved fcetus is somewhat redundant and masks the real shape of the 

 kidneys, causing them to appear larger and more plump than actually they are. Upon this 

 thick investment of the kidney are the impressions of the duodenum at the upper pole and of 

 the colon in the rostral half of the mesal border on the right side, and of the colon again on the 

 left side along its mesal border caudad. But the kidneys themselves show no traces of contact 

 with these organs upon the removal of their capsules. The fascia renalis has much the same 

 arrangement as Gerota * has described for man. Its ventral layer crosses the aorta and post- 

 cava to become continuous with that of the opposite side. The dorsal layer is easily stripped up 

 from the sheath of the hypaxial muscle to near its mesal border, where it becomes firmly adher- 

 ent. Somewhat lateral to the kidney the two layers unite and are continued as the endabdominal 

 fascia. Rostrad the adrenal is included between the layers, which fusing are continued as 

 the very thick fascia on the abdominal surface of the diaphragm. Caudad they are continued 

 dorsal and ventral to the ureter, and here fat appears between them for the first time. They 

 now become thinner and difficult to follow and apparently are lost as in man in the areolar tissue 

 of the region. 



Beneath the fascia renalis the kidney is invested by a thin transparent tunica fibrosa. This 

 is without much difficulty resolvable into two layers, one relatively thick and strong of super- 



1 Beauregard and Boulart. Recherches sur les appareils genito-urinaires des Batenopterides. Jour, de 1'Anat. ot de la Phys., An. 

 XVIII, 1882. 



2 Daudt, Wm. Beitrage zur Kenntins des Urogenitalapparates der Cetaceen. Jena, Zeitsch. f. Naturwiss., Bd. XXXII, 1898. 



3 Eschricht. Zool.-anat.-phys. Untewuchungan iibar die nordischen Waltiere. Leipzig, 1849. 



* Gerota, D. Beitriige zur Kcatniss des Befestigungsapparates der Niere. Arch. f. Anat. und Entwickel., Jahr. 1895, p. 265. 



