70 



,Nr. 7. Obelia geniculata (L.). (Inaba 1S90 Fig. 17. 18, 19.) 



Trophosome. Stfiu 10 mm liigh, distinctly wavy, with constrictions at the points of cui- 

 vature, the perisarc swollen and projecting directly below the constriction and giving 

 rise to a hranch. Hydrotheca conical in shape, a little longer than broad, with straight 

 border, the short stalk consisting mostly of three rings, standing out at an angle from 

 the stem and gradually becoming smaller upwards. 



Gonosome. Gonotheca bottle-shaped, borne on hydrorhiza or axils, stalk short with three 

 or foiir rings. Medusae completing their development in the gonotheca; bell shallow, um- 

 brella-shaped, with 24 marginal tentacles when freed. 



Locality. Moroiso Bay, Sagami Sea, on Alaria pinnatifida. 



Date. Gonothecae found in July. 



Fig. 26. Obelia geniculata (L.) 

 Typische Form. (I. 1890 Fig. 19.) 



Fig. 27. Obelia geniculata (L.). 

 Schlanke Varietät mit Gonotheken. (1. 1890 Fig. 21.) 



This species can be easily distinguished by its peculiar strueture. Hincks mentions 

 two varieties; one small and pure white (transparent?) of stunted growth, the other large 

 and with slighter curvatures. My specimen belongs to the first variety and resembles closely 

 the figures of Eucope diaphana by L. Agassiz (Nat. Hist. U. S. Vol. 4 tab. 34 figs. 1 — 9). 

 which is, according to Hincks, identical with 0. geniculata (L.). 



There are one or two ring-shaped furrows in the lower part of each Joint of the 

 stem, and there are rarely two hydrothecae side by side in the same axil. " (Inaba 1890.) 



