HYDROIDA II 



149 



throughout three hydrothecse between the origins of two branches on the same side of the stem; in 

 the two smaller colonies, on the other hand, the number varies from two to five, but these colonies 

 are at the same time irregular in the whole development of the branches in several places. The divi- 

 sion of the branches into internodia is highly irregular; there may be from two to 

 nineteen hydrothecse on the branch internodia. The hydrothecse are set in two 

 opposite rows; their symmetrical plane coincides with the broad plane of the bran- 

 ches, which is everywhere vertically placed, i. e. parallel with the axis of the stem. 

 The distance between two hydrothecse on the same side of the branch is very great, 

 as a rule about i J / 2 times the length of the hydrotheca itself. The hydrotheca (fig. 

 LXXIX) is not particularly deeply imbedded in stem or branches; the distal third 

 of the adcauline wall is free; the free part of the adcauline wall is straight, or not 

 infrequently curving slightly upward. The opening plane of the hydrotheca is pa- 

 rallel with the branch axis. The aperture is round, the margin exhibits indication 

 of a pair of broad lateral teeth, further accentuated by the abcauliue sinus in which 

 the large single opercular plate is fastened. The structural character of the polyp it 

 was impossible to investigate, owing to the state of preservation of the material. 



These colonies appear in the main to agree with the Pacific species Thujaria 

 distans established by Fraser (1914 p. 197, pi. 32, fig. 123). There are, however, 

 lacunae in Fraser's description, so the identity cannot be determined with certainty. 

 Fraser's species has often secondary dichotomous ramification of the branches; 

 this must be considered as due to difference in age. On the other hand, the hydro- 

 thecse in Thujaria distans appear to have a larger free portion; Fraser states 

 "about one-half free", and the figures appended, which are not very carefully drawn, even show hydro- 

 thecse more than half free; they give, moreover, no clear impression as to the character of the hydro- 

 theca aperture, which is likewise somewhat vaguely treated in the diagnosis: "margin without distinct 

 teeth but rather bilabial". Only when a conscientious description of the Pacific species is available 

 will it be possible to decide whether the colonies here found in the North Atlantic should be referred 

 to the same. 



Family series Proboscoida (Broch). 

 Family Campanulariidae. 



The hydrothecse are radially symmetrical, bell-shaped, without closing apparatus, and provided 

 with a basal chamber separated off from the distal main part of the hydrotheca by a diaphragm, or 

 by a simple ring-shaped thickening of the wall. The polyps can withdraw entirely into the hydro- 

 thecse. The hydranth has a club-shaped proboscis, attached by a narrow base to the body of the polyp 

 above the tentacle crown; the gastral endoderm is homogeneous, the stomach part not divided into 

 separate regions. The colonies are stolonial or sympodial. 



Fig. LXXIX. 



Thujaria sp. aff. distans 



from "Ingolf" St. 85. 



Part of a branch. 



(X40). 



