170 EXPEDITION OF THE "ALBATROSS," 1899-1900. 



A number of young individuals between 2 mm. and 4 mm. in length were found 

 by the " Albatross " among the Paumotus and Society Islands. Those 2 mm. 

 in length (Fig. 43) possess but one primary axial polypite, from the side of 

 which there arises a single tentacle. This tentacle bears a number of wart- 

 like nematocyst-bearing swellings upon one side. The float at this stage is 

 simple and terminal, and the air-sac is oval and communicates with the outer 

 world by means of an apically situated pore. The gastric portion of the 

 axial polypite contains a number of disk-shaped hepatic villi. Two very 

 small evaginated protuberances are seen projecting outward from the ven- 

 tral floor of the float. These are the beginnings of the secondary polypites 

 and tentacles, which in the adult are much larger and more numerous than 

 the primary. In specimens about 4 mm. in length (Fig. 44) the secondary 

 tentacle has become larger than the primary, and there are several feeding 

 polypites of the secondary set budding outward around its conical base. 



Unlike the adult, these young individuals possess the ability to sink 

 beneath the surface ; a feat which they accomplish by extruding a bubble 

 of gas through the pore of the float. In a few minutes the gas regenerates, 

 and then the animals rise to the surface. Figure 44 shows the creature in 

 the act of forcing a gas bubble out of the pneumatophore, and it will be seen 

 that the muscular inner wall of the air-sac exhibits an annular contraction. 



S'' ; Station 13 ; September 5, 1899 ; N. Lat. 9° 57', W. Long. 137° 47'. 

 grf. u 14 . u 7^ a « 6° 41', " 137°. 



S'; " 16; " 9, " " 2° 38', " 137° 22' 



is' 1 ; " 173 ; November 4, " S. Lat. 18° 55', " 14fi° 32°. 



S''; January 22,1900; Lagoon of Wotje, Marshall Islands. 



S ; Fiji Islands; 1897-98. 



CTENOPHOR.SI. 



Pleurobrachia ochracea, sp. nov. 



Plate 13, fig. 58. 



The animal is egg-shaped and about 12 mm. in length. The body is 

 somewhat compressed in the diameter perpendicular to the tentacular axis. 

 The aboral pole is quite blunt. The outer surface is smooth and there 

 are no papillas. The apical sense organ is quite large and contains a mass 

 of spherical otoliths. There are eight meridional canals which extend 



