100 ATBACTYLID^E. 



centre of which rises a short proboscis. They are held al- 

 ternately elevated and depressed, and each of the drooping 

 arms bears near its base one of the curious bosses that 

 constitute so striking a feature of this zoophyte. They 

 consist of a number of elongate bean-shaped thread-cells,, 

 piled together so as to form silvery-white prominences on 

 the lower side of the tentacles a girdle of pearls round 

 the base of the tentacular ring. 



The gonophores are of great size and are supported on 

 a rather long peduncle, the base of which is invested by 

 the polypary. 



They contain a single sporosac, from the bottom of which 

 proceed four much-branched vessels, terminating near the 

 top in blind extremities and immediately enclosing the ova, 

 which fill with a dense mass the interior of the cavity. I 

 have not detected any traces of a manubrium. The ecto- 

 theca, or outer envelope of the gonophore, is filled with 

 the long bean-shaped thread-cells, which are also present 

 in amazing numbers in the ectoderm of the coenosarc. 



H. MARGARICA, HinclvS. 



ATRACTYLIS MARCARICA, Hincks, Ann. N. H. for Jan. 1803, (ser. .3) vol. xi. 

 45, pi. ix. fig. 4. 



Plate XIX. fig. 1. 



STEMS invested by small, somewhat funnel-shaped exten- 

 sions of the polypary ; POLYPITES white, with a tinge of 

 yellowish colour on the thickest part of the body, slightly 

 retractile, tapering downwards, swollen in the centre, 

 and expanding towards the upper extremity, with about 

 30 tentacles, alternately elevated and depressed, and 

 webbed at the base ; GONOPHORES produced singly or in 

 pairs close to the polypites, globular, the peduncle tapering 

 downwards and enclosed at the base by a small chiti- 

 nous cup. 



