386 FUNAFUTI ATOLL. 



In the ectoderm there are present narrow oval nematocysts, 

 0'14 mm. long, but zooxanthellre are absent. Slightly branched 

 canals arising from the ectoderm are present in the mesoglcea, 

 but are not at all numerous, though somewhat more abundant in 

 the lower part of the column. In the rarity of ectodermal canals 

 the species under consideration agrees with Z. jukesii, H. & S., 

 and as in that species lacunae are fairly numerous. Small cell- 

 groups and isolated rounded or spindle-shaped cells, produced into 

 radially running processes, also occur in the mesogloea. Nemato- 

 cysts are present in the ectodermal canals in small numbers. In 

 the lacunse there occur very definite, small, rounded or oval bodies, 

 often in considerable numbers. In general appearance these re- 

 semble nematocysts, but are apparently quite homogeneous in- 

 ternally and show no trace of threads. 



The entoderm is thin, and contains nematocysts and numerous 

 zooxanthellse. The entodermal circular musculature is weakly 

 developed, and supported by minute mesogkeal plaitings. 



Capitulum. The ectoderm here is ridged and thicker than 

 that of the column-wall. It contains nematocysts. 



Sphincter muscle. The double mesogkeal sphincter muscle is 

 well developed. Its upper portion is about three times the length 

 of the lower. The latter consists of a single row of cavities, 

 rounded in shape and larger than those of the upper portion 

 which are small and compressed and not arranged in a single row. 

 In both, the muscle fibres are supported on plaitings of the meso- 

 gloea. 



Tentacles. The ectoderm is thick and is crowded with enormous 

 numbers of small sausage-shaped nematocysts, '01 mm. in length, 

 zooxanthellre are absent. The ectodermal musculature, longitu- 

 dinal in direction, is moderately strong and supported on small 

 plaitings. The mesoglcea is thin, and contains only small scattered 

 cells. The entoderm is a very thick layer. It contains numerous 

 nematocysts similar to those of the ectoderm, and zooxanthelhe 

 are also numerous. The circular entodermal musculature is very 

 weak. 



Disc. The ectoderm of the disc is ridged. It is in general 

 similar to the ectoderm of the tentacles, but nematocysts are here 

 not so numerous. The mesoglcea contains isolated cells and cell- 

 groups. In the entoderm numerous zooxanthelhe are present. 

 The musculature of the disc is weak. 



(Esophagus (Plate xxv., fig. 2). The ectoderm is thrown into 

 distinct longitudinal folds. The groove is wide and well marked. 

 The ectoderm contains nematocysts, and here and there in the 

 basal parts of the cells there occur groups of refractive yellow 

 (pigment 1) granules. The mesogloea forms a uniformly thin layer. 

 The entoderm is also thin, and contains zooxanthellge in no great 



