Some Northern Hydroid Zoophytes. 



229 



of the hydrotheca. They are almost uniform in width throughout, and are 

 scoop-shaped, opening upwards and towards the internode. The margin is 

 smooth. The mesial sarcotheca is short, adnate to the lower sixth of the 

 hydrotheca, and free for half its length. It also is scoop-shaped, and its rim 

 is entire. Three cauline sarcothecse, similar in structure to the supracalycine 

 sarcothecse, occur at the base of the hydroclade process : two anterior, one 

 above and one below. 



Gonosome. — Gonangia are present on the stem and branches. They are 

 unprotected by special arrangements of branches, are ovate in shape, with a 



Fig. 6. 

 Portion of hydroclade, with hydrothecpe, of HaUcornaria Integra. 

 £. s., supracalycine sarcotheca. h., hydrotheca. 



x 50. 



i. sept., internodal septum. 

 n., node. 



i-th. r. 

 m.s., 



intrathecal ridge. 

 mesial sarcotheca. 



horseshoe-shaped aperture, and arise from the anterior of an internode close 

 to the hydroclade process, at the base of the distal cauline sarcotheca 



Dimensions. 

 Stem internode, length 



diameter . 

 Hydroclade internode, length 

 Hydrotheca, depth 



diameter at mouth 



Gonangia, 



length 



greatest diameter 



071— 0-75 mm. 

 0'20 mm. 

 0-69— 073 mm. 

 0-43—0-50 mm. 

 0-29 mm. 

 1-29— 154 mm. 

 0-68— 0-70 mm. 



