312 bulletin: museum of comparative zoology. 



0. longissima, are very often found on floating eelgrass, hence as long 

 as the eelgrass fragments are of sufficient size to form a good basis of 

 support for the stolon, it is not especially remarkable that 0. geriicu- 

 lata should remain in good condition when floating. However, in 

 hundreds of cases where 0. longissima has been seen floating, there 

 has been no great difference observed from the regular type (that 

 may be because it very generally is found attached to floats, etc., 

 where it is near the surface at all times), but in these specimens 



Fig. 75. — Obelia geniculata: 



Fig. 76. — Obelia genlculata. 



there are some unusual features, that may have been caused by 

 a certain tendency towards orientation disturbed on account of a 

 change in the position of the support. This change does not show itself 

 in the hydranths themselves since they seem perfectly normal, pos- 

 sibly because the hydrotheca pedicels have sufficient adaptability to 

 allow for sufficient change. In the stems, however, there is variation. 

 Some of them are quite typical (Fig. 75) but a large number of them 



