HYDROIDA. — BALE. 47 



branches, which mostly occur on the upper half or two-thirds of 

 the stem, are usually in two series and alternate, nearly in the 

 same plane, and attaining up to eight or ten inches in length ; 

 tliey often face in the same direction but this character seems 

 inconstant. Secondary branches are abundant, and a few small 

 ones of the third order were observed. There is however, much 

 irregularity in the ramification, especially in the distance apart 

 of the branches, which may be from one to three or four inches. 

 The proximal part of a branch may include as many as twenty 

 internodes on which only sarcotheca? are borne. While the 

 branches have their origin in the hydrocladiate tube they do not, 

 as in all the preceding species, take the place of a hydrocladium, 

 but, at least in the few young branches which I examined, they 

 are supported on the same internode with a hydrocladium, and 

 opposite to it. 



No other species, so far as I am aware, shares in the peculiar 

 construction of the hydrotheca which is found in the form before 

 us. The aperture by which the cavity of the hydrotheca com- 

 municates with that of the internode is not situated as usual at 

 the proximal end of the hydrotheca, but at the opposite extremity, 

 just under and between the lateral sarcotheca?. Above this entry 

 is the intrathecal ridge, which runs directly backwards half 

 through the hydrotheca, and around which the latter is abruptly 

 recurved, being thus divided into two compartments, a narrow 

 proximal one, and a much wider distal one. Thehydranth there- 

 fore will be completely doubled upon itself around the intrathecal 

 ridge. It is interesting to note that the lateral sarcotheca? are 

 doubled back in a somewhat similar fashion, their openings into 

 the internode being far forward so that the sarcostyles will be 

 recurved like the hydranths. In the presence of a sarcotheca 

 behind each axil we have a feature usually characteristic of 

 Halicoruaria. The two cauline sarcotheca on the front of the 

 rachis are set further apart than in most species, the inferior one 

 being close to the lowet end of the internode. 



The corbalas are beautiful structures, varying in length from 

 about half to three-quarters of an inch, one specimen measuring 

 seven-eighths, or considerably larger, I believe, than any other 

 species is known to possess. They are when mature of a deep 

 reddish-brown colour, and of firm robust texture, not subject to 

 distortion in drying. The openings near the base of the leaflets 

 are very small and entirely occupied by the modified hydrotheca?, 

 which do not in any way resemble those on the hydrocladia' 

 being very small, straight, and tubular, with the margin irregu- 

 larly crenate, and accompanied by a pair of very similar lateral 

 sarcotheca?. A striking feature of the corbula is the double series 

 of large convex secondary leaflets which rise from the surface 



