vol. i.i Torrey. — Hydroida of lite Pari fir Coast. 67 



upon the direction of hydranth buds. The farther the stems 

 diverge from the vertical, the more closely do the hydrothecae 

 of each pair crowd each other on the upper side of the stem. 



These facts, together with those which relate to the habit of 

 8. argentea (p. 68), render it probable that geotropism is to 

 some extent an efficient cause of the habits of various desmoscyphus 

 forms. It is possible that the same explanation may be applicable 

 to the habits of other colonial coelenterata, especially those cords 

 in which the mouth axis of each polyp lies in a plane passing 

 through the axis of the colony. 



Thuiaria group. 



Hydrothecae more or less alternating, in two rows, closely placed, and 

 many to an internode. 



Sertularia argentea E. & S. 



PI. VIII. Figs. 70, 77. PI. IX. Pigs. 78, 79. 



Sertularia argentea, Ellis and Solander, Nat. Hist, curious and uncom- 

 mon Zooph., etc., 1786, p. 38. Clark, Trans. Conn. Ac, 1876, 

 III, p. 257. 



Thuiaria argentea. Nutting, Proc. Wash. Ac. Sc, 1901, III, p. 184. 



Distribution. San Francisco, Tomales Bay and Patrick's 

 Point, Cal., shore rocks. Santa Barbara, Cal. (Clark). Puget 

 Sound, Wash., and Yakutat, Al. (Nutting). "Ostend (Van 

 Ben.) ; mouth of the Elbe (Kirchenpauer) ; Greenland (Fabr. and 

 Morch); North Cape, in 30-50 fath. (Sars) ; Southern Labrador, 

 Caribou Island, in 8 fath., not common (A. S. Packard, Jr.); 

 Nova Scotia (Dawson) : Grand Manan, common in 4-6 fathoms, 

 attached to stones (Stimpson) ; Massachusetts Bay (Agassiz) ; 

 South Africa (Busk)." (Hincks, '68.) Greenland (Levinsen). 



All the colonies in the collection are of the small variety 

 mentioned by Hincks as occurring between tides. The tallest 

 stem is 35 mm. long. The hydrothecae vary in shape and 

 position on the branches; the two teeth are usually of equal 

 length. Gonothecae are present on some of the San Francisco 

 colonies, several with acrocysts (Jan. 22, 1902). The dimensions 

 of the gonothecae as well as the length of their horns, vary 

 considerably. The acrocysts are borne by broad gonothecae 

 with long horns. All gonothecae are compressed. 



