EISEN 



Intestine with very minute chloragogen cells. Spermathecae join the 

 intestine in V ; diverticles as long as the ampullar part, club-shaped ; 

 ampulla inflated and sac-like ; duct strongly muscular. Sperm-ducts 

 narrow and probably short. No atrium exterior to the bulb. But 

 inside the latter we find an enlargement of the sperm-duct, of similar 

 form and structure as an ordinary atrium, but without the atrial glands. 

 Below this enlargement there is a swelling of the walls of the duct 

 containing a large number of thin and slender penial glands opening 

 in the very apex of the sperm-duct. Penial bulb with numerous 

 large glands opening around the penial pore. No accessory 

 glands. Sperm -sacs apparently small. Lymphocytes small, ovoid, 

 with pointed ends. Color of alcoholic specimen deep yellow, no 

 pigment. 



Locality. Bering Island, Bering Strait, Alaska. Collected by 

 Dr. Anton Stuxberg, Vega Expedition under Baron Nordenskiold, 

 August 15, 1879. A single specimen. 



Characteristics. Although the want of specimens prevents a 

 thorough examination and leaves many points undetermined, yet the 



few characters known are so 

 prominently characteristic that 

 the species cannot be con- 

 founded with any other thus 

 far described. The absence of 

 both atrial and accessory 

 glands at the same time is a 

 rare occurrence. In many 

 respects the structure of the 

 efferent apparatus reminds us 

 of M.pedatus. The differ- 

 ence between the two species 

 is however great enough. In 

 M. pedatus the large glands 

 at the base of the sperm-duct 

 are free and not enclosed in 



the bulb. In our present spe- 

 FIG. 7i. Mesencliytroeus bertngensts. 



cies these glands are entirely 



enclosed in the penial bulb. Neither species possesses atrial glands. 



DETAILED DESCRIPTION. 



Brain (fig. 31, e). Posterior margin almost straight, the general 

 form of the brain rounded, as in fig. 31, e. In the specimen ex- 

 amined the two sides of the brain are somewhat unequal. 



