HYDROZOA, SCYPHOZOA, ACTINOZOA, VERMES WHITELEGGE. 387. 



numbers. The ectoderinal musculature, longitudinal in direction, 

 and the entodermal, circular in direction, are both weakly developed. 

 Mesenteries (Plate xxv., fig. 2). The mesenteries are slender, 

 and have the normal brachycnemic arrangement. The reflected 

 ectoderm of the oesophagus forms ridges (8-11 in number) along 

 the two faces of each perfect mesentery, and is limited to the 

 inner half of the radial extent of each mesentery. Below, the 

 peripheral folds of the reflected ectoderm are continued on as the 

 mesenterial filaments. These are at first V-shaped in section, 

 but lower down the free limbs of the V soon disappear, and the 

 ectoderm of the filament assumes a rounded bulbous form. At 

 the same time the entoderm becomes thickened immediately below 

 the filament, givinsr rise to a second bulb-like swelling. The ecto- 

 derm of the filament contains numbers of deeply-staining gland- 

 cells, and in its deeper part occur numerous small granules which 

 stain slightly with eosin. Rod-shaped nematocysts also occur in 

 the ectoderm, as well as in the thickened entoderm. The mesen- 

 terial filaments continue to near the base of the column, and are 

 considerably folded. The mesogloea of the mesenteries is a thin 

 layer, which, however, becomes somewhat thickened just before 

 joining the body-wall. In this outer thickened part is situated 

 the single basal canal of the mesentery. In the lower part of the 

 column, the mesogloea of the mesenteries is somewhat thicker and 

 the basal canals are larger. The entoderm of the mesenteries is 

 a thin layer containing zooxanthellse, which are usually much 

 more numerous on one face of the mesentery than on the other. 

 Nematocysts are sparingly present in the entoderm. The parieto- 

 basilar muscles are supported on mesoglceal plaitings, and are well 

 developed. The longitudinal musculature is fairly well developed, 

 and supported on small plaitings. 



Gonads, Gonads were not present in any of the specimens 

 examined by us. 



This species is closely related to Z. jukesii, H. & S., but is 

 to be easily distinguished by, among other points: (1) its smaller 

 size, (2) its green coloration, (3) the absence of nematocysts from 

 the entoderm of the tentacles. 



GEMMARIA WILLEYI, sp. nov. 

 (Plate xxiv., figs. 1 and 4). 



Form. Body-wall opaque, encrusted with foreign matter and 

 minutely granular. Surface even when extended, transversely 

 wrinkled when contracted. Coenenchyme incrusting, forming 

 broad expansions or band-like stolons. Column often slightly 

 swollen in the middle. The capitular region greatly expanded, 

 with about forty very short radial ridges. Disc large, radiately 

 ridged. Oral cone prominent, aperture oblong. Tentacles short, 

 subequal, eighty in number, arranged in two cycles. 



