58 



EISEN 



Intestine with very minute chloragogen cells. Spermathecas join the 

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

 ampulla inflated and sac-like ; duct strongl}^ 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, 1S79. 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- 

 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. 



Fig. 31. Mesenchytrceus heringensis. 



