REPORT ON THE ANTIPATHARIA. 197 



between the distal ends of the hyaline gland cells, and sometimes nearly reach to the 

 base of the layer. The outline of the individual cells is, however, not well defined in 

 borax-carmine preparations. In sections stained with hasmatoxylin the appearance 

 is quite different, and some of the small granular gland cells are well defined. In such 

 cases the structure of the stomodaaal ectoderm closely resembles that of Actiuiaria, 

 excepting for the apparent absence of nematocysts. The surface of the stomodajum 

 is composed of slender, ribbon-like, ciliated cells, usually separated from one another by 

 delicate, thread dike, sensory cells. The nuclei of both these types of cells are situated 

 about the middle of the layer, and on account of their great affinity for the stain, 

 appear as an irregular dark band across the middle of the ectoderm. Just beneath 

 the surface numerous small oval gland cells are pushed in between the ciliated 

 " Stiitzzellen " at irregular intervals. These vary from 875 to 10'3 fJ- in length, 

 and from 3"2 to 675 p in breadth. They stain deeply in hsematoxylin, and are 

 seen to be filled with comparatively large rounded granules. On this account this 

 type of cell will be distinguished as the granular gland cells. The granular gland 

 cells appear to be connected by a delicate stalk or fibre to the base of the ectoderm. 

 Between the proximal ends of the non-glandular cells, large, oval, hyaline gland cells 

 occur in considerable numbers, forming the chief feature of the lower portion of the 

 epithelial layer of the ectoderm, and resting directly on the nervous layer. The 

 hyaline gland cells vary from 24-3 to 37*5 /x in length, and from 107 to 12-5 /x 

 in breadth. No ectodermal muscular fibres have been observed in the stomodseum. 



Mesoglcea. — The mesogloea in Actiniaria consists of a moderately thick layer, 

 presenting a uniform ground substance in which numerous fibres are distributed. In 

 Hexactinise the layer also includes numerous stellate or spindle-shaped connective- 

 tissue cells, but these are either absent altogether or much reduced in importance in 

 Cerianthidaa and Zoanthidse. In the Antipathinse the mesogloea is usually very thin, 

 and does not contain any stellate or spindle-shaped connective-tissue cells. In 

 Antipathella subpinnata this layer has an average thickness of 3 /x in the 

 tentacles, and does not attain a greater thickness than 9 /* in any part of the polyp. 

 It usually appears structureless in section, but sometimes irregular longitudinal lines 

 may be recognised within its substance. These may indicate the presence of fibres, 

 or may, perhaps, be due to the action of hardening reagents. In any case such 

 striations do not appear to be always present. 



Entoderm. — In Actiniaria the entoderm consists largely of a layer of cylindrical 

 epithelial cells in which symbiotic Algae are frequently imbedded. Each epithelial cell 

 is intimately connected at its base with a slender muscular filament. A few nematocysts 

 are also present, and also a variable supply of hyaline and granular gland cells. Whilst 

 a distinct nervous layer is not always demonstrable, the whole of the epithelial cells 

 appear to end basalwards in muscular or nervous threads, and thus constitute more 



