20 SYDNEY J. HICKSON AND F. H. GRAVELY. 



Each Intel-node of a pinnule bears one hyclrotheca at its distal extremity, but 

 each iuternode of a branch bears three hydrothecas, one at the distal extremity, and 

 the other two at intervals of one-third and two-thirds from the proximal end. 



The hydrothecse of the pinnules (fig. 19) are about 0'5 mm. in depth, 0'22 mm. 

 in their greatest diameter, and 0'17 mm, in diameter at the mouth, and have three 

 opercular flaps (fig. 19, op.) 0'09 mm. in length. They are somewhat shorter than 

 this in the proximal regions of the pinnules. The two proximal hydrothecse of 

 the internodes of the branches are decidedly shortened as regards that part of 

 their length which is not adnate. The distal hydrotheca of each iuternode of the 

 branches is nearly straight and barrel-shaped. A single straight hydrotheca, which is 

 not adnate to any part of a hydrocaulus, is situated between the bases of each pair of 

 branches (fig. 20, hth.). Apart from these, the main axis bears no hydrotheca}. 



A remarkable feature of the hydrauths is the presence of a loose sheath of 

 ectoderm (fig. 19, ccf.) enveloping the base. The hypostome is conical and 

 surrounded by about fifteen tentacles. 



Gonosume. Only female gonothecte (fig. 19, f/t/i.) have been observed. They 

 are 1 X 0'5 mm. in size, ovate, smooth, sessile, and attached below the bases 

 of the hydrotheca) of the pinnules. The gonothecse are all empty, none of the 

 gonophores being preserved. The planulse are developed in spherical or somewhat 

 pear-shaped acrocysts (fig. 19, ac.), 0'4 mm. in diameter. 



This species seems to be quite distinct from any that has yet been described. 



SERTULARELLA PLECTILIS. 

 (Plate III., fig. 21.) 



LucitlitiL's.'W.Q., No. 6 hole, February 15th, 1902 ; 130 fms. W.Q., McMurdo 

 Bay, February 20th, 1902; 20 fms. 



Several large, detached, tangled masses of this hydroid were found in the first- 

 named locality ; but in the second locality only a single small colony 12 mm. in 

 height attached to the stem of Campanularia verticillata was obtained. 



Hydrosome, The hydrocauli are all extremely slender, not exceeding 0'12 mm. 

 in diameter, irregularly branched, and as they reached us in an inextricable tangle. 

 The internodes are about 0'6 mm. in length. The branches arise immediately below 

 the hydrothecse (fig. 21). A single hydrotheca is situated at the distal end of 

 each internode. As many of them are reduplicated (fig. 21, ;. /it/i.), they vary 

 considerably in length. The original length of each hydrotheca appears to be 

 0'4 mm., but one showing four reduplications is O'G mm. The greatest diameter 

 is 0'15 mm., and at the mouth 0'13 mm. The wall is adnate to the hydrocaulus 

 for about one-third of its original length. It is extremely thin. The margin has 

 three opercular flaps, O'OG mm. in length. About fifteen tentacles surround the 

 bluntly conical hypostome of the hydrauths. 



