200 THE VOYAGE OF H.M.S. CHALLENGER. 



The only part of which sections were obtained consists of an elongate reproductive 

 capsule, having a flattened oval outline about - 23 x - 14 mm. in diameter. At irregular 

 intervals a short blunt lobe is pushed out from one side or the other, and .distinct indica- 

 tions of an annular constriction have been noticed in one specimen. The structure is 

 similar in all the sections examined. The wall of the capsule (PI. XV. fig. 6) consists 

 of fibrous tissue in which a large number of small oval germinal cells are imbedded. 

 More internally the germinal cells are collected into groups of variable size, still 

 supported by a fibrous stroma, and show various stages of subdivision. Apparently each 

 germinal cell gives rise to a cluster of spermatozoa in most instances (PI. XV. fig. 6, I), 

 but in one of the specimens ova have also been observed. The ova are small and 

 contain a relatively large nucleus with a central large nucleolus and a number of small 

 ones distributed around the periphery. 



A small infusoriform parasite has also been met with on several occasions, both 

 associated with the larger vermiform one and in other specimens. It is pear-shaped or 

 oval in outline, and usually contains a large circular hyaline area together with a number 

 of densely stained masses, which are irregularly distributed through the protoplasm. In 

 some of the sections of it the surface j:>rotoplasm appears more transparent and obliquely 

 striated as if clothed with cilia. This form is usually met with in the angle between 

 the body-wall and the skeletal sheath, or at the extreme apex of the ccelenteron in the 

 oral cone. A specimen is shown in the latter position on the left half of PI. XIII. fig. 5. 



Antipathella minor. 



The ectoderm of Antipathella minor contains the same histological elements as 

 that of Antipathella subpinnata, but the individual cells are grouped somewhat 

 differently. The ectoderm of the tentacles consists as usual of batteries of nematocysts 

 and groups of hyaline gland cells arranged alternately. The surface of the layer is 

 raised into irregular rugae, which are arranged transversely in interrupted series around 

 a tentacle. The rugse vary from 0"116 to 0'175 mm. or more in length, and have a mean 

 diameter of about 0'03 mm. near the centre, but taper towards each extremity. In 

 longitudinal sections of a tentacle the transverse rugae are indicated by crenations of 

 the surface. Unlike the usual arrangement in Antipathella subpinnata, the batteries 

 of nematocysts are here the most prominent cells of the ectoderm, each raised ridge 

 corresponding to an elongate battery of nematocysts. In sections the batteries are seen 

 to form wedge-shaped groups of cells, limited laterally by two lines which gradually 

 converge towards the base of the layer. The broad end of each wedge-shaped area is 

 occupied by a number of closely-arranged nematocysts, which occupy the outer third of 

 the band. Beneath the adult nematocysts a large number of deeply -stained oval nuclei 

 occur, which are evidently imbedded in slender thread-like cells. The groups of 



