62 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. XIV. 



thin membranes and the thickened walls of the uteri. The largest was 

 approximately 4 mm. in length and well advanced in development. 

 By a most unfortunate accident, these embryos, after being removed and 

 set aside for special study, were totally destroyed. 



Mere gross dissection, however, is sufficient to show that the re- 

 productive system of Canolestes is markedly different from that of the 

 primitive polyprotodonts. 



MALE GENERATIVE ORGANS. 

 Plates VIII-X. 



The prostate gland is exceedingly large, relatively larger than in 

 any other marsupial known to me and therefore probably larger than in 

 any other mammal. It is a prominent ovate body occupying practically 

 the entire space in the posterior part of the body cavity and extending 

 from the kidneys to the pubis. In a normal adult with a body length 

 of 113 mm., it measures 16 mm. in length and n mm. in greatest diam- 

 eter. The bladder, which is small and inconspicuous in comparison, is 

 situated on the dorsal surface of the prostate somewhat caudad of its 

 anterior expansion and thus scarcely visible from the ventral aspect. 

 The gland is not tapering and radiciform as usual but is only slightly 

 smaller posteriorly than anteriorly and the narrow urethral canal makes 

 exit from its walls abruptly on its dorso-caudad surface. The prostate is 

 enclosed in a thin membranous or slightly muscular covering of trans- 

 verse fibers. The thickened portion consists of numerous slender cylin- 

 ders of glandular tissue radiating from the urethral canal to the periph- 

 ery. The urethra in its course through the prostate is quite small and 

 is longitudinally plicated on its inner surface (PI. X, Fig. 5). 



The ureters and vasa deferentia enter a groove between the base 

 of the bladder and the prostate, the former going to their orifices on the 

 dorsal side of the bladder near its neck and the latter turning sharply 

 caudad into a groove in the prostate to a common opening into the ure- 

 thra a short distance beyond its enclosure by the prostate (PI. X, Fig. i). 

 The vasa deferentia have the usual course, leaving the base of the testes 

 and diverging to enter the body cavity and pass dorsally on each side of 

 the colon to their terminations. Before entering the raphe in the 

 prostate they are somewhat enlarged and slightly convoluted. There 

 are no obvious seminal vesicles. 



From its exit from the prostate the urethra continues as a slender 

 tube for about 5 mm. to its bulbous portion where it enlarges and re- 

 ceives the ducts of the Cowper's glands. This bulbous urethra is short 

 and wide and has a slight forward projection or cul de sac on its ventral 



