386 DISCOVERY REPORTS 



between the two investments and a prolongation of this cavity penetrates as a blind 

 caecum between the epididymis and the testis. In Mesoplodon the testis lies in an 

 inguinal cavity resembling a cremaster sac. 



The vasa defer entia 



The vasa deferentia (Fig. if) lie within the fibrous ligamentum latum which is 

 attached centrally along the proximal part of the dorsum of the neck of the bladder and 

 laterally contributes to the genital cord (Fig. i g). The posterior border of the liga- 

 mentum latum thus forms an arc between the neck of the bladder and the genital cord, 

 through which the ureter emerges from its peritoneal coverings and passes upwards and 

 forwards on to the neck of the bladder. The anterior border of the ligamentum is 

 thicker than the posterior, and carries the vasa deferentia throughout the proximal part 

 of their course. 



The vasa deferentia are a pair of small sacculated ducts lined by a much folded columnar 

 epithelium and surrounded by a thick fibrous investment containing blood vessels. In 

 sections taken from the middle of the course of the foetal ducts no muscular tissue was 

 seen. After leaving the cauda epididymis, which consists only of an abundantly con- 

 voluted duct continuous with the vas deferens, each vas passes transversely in the anterior 

 border of the ligamentum latum towards the middle line of the body. In the small 

 foetus (1*23 m.) this part of the course of the vas deferentia measured 2-5 cm. The ducts 

 curve very slightly forwards during the transverse part of their course, and on reaching 

 the middle line, turn abruptly backwards and run close together upon the neck of the 

 bladder. On reaching the junction of the neck of the bladder with the prostate, the two 

 ducts enter the fibrous wall of the urinary canal and converge inwards through it. In 

 this part of their course they have no sacculations and are of exceedingly small calibre. 

 They open as already described upon the verumontanum. 



As appears to be the rule in the Cetacea no seminal vesicles were found upon the 

 course of the vas deferentia. Daudt, however (p. 297), makes brief mention of 

 structures which he calls " samenbereitenden Organe" lying against the epididymis. 

 In Mesoplodon Anthony describes a small caecum on the testicular part of the course of 

 the vas deferens projecting between the canal itself and the wall of the vaginalis. This, 

 however, is probably not a reduced vesicula seminalis, owing to its proximity to the 

 epididymis. Actually the figure that Anthony gives does not show the structure as a 

 caecum at all, but as one of the convolutions of the vas deferens itself. Le Danois also 

 described a diverticulum on the vas deferens of Kogia which he regarded as a reduced 

 vesicula seminalis. This structure was also situated high up on the course of the vas 

 deferens, far removed from the urethral region. In Neomeris phocaenoides, according to 

 Chi Ping (1926), the lower ends of the vasa deferentia of the two sides converge in the 

 middle line to form a single ductus ejaculatorius, and at their meeting point there is a 

 median vesicula seminalis situated between them. 



