7. Anthozoa (incl. Hydrocorallia). A. Zoantharia. 43 



and pigment granules in virtue of which they replace one another in Para- 

 zoanthus does not exist in these species. 



Groselj has investigated the nervous system of Cerianthus, Actinia, Adam- 

 sia, Aiptasia, Ragactis, Heliactis, Bunodes and Ilyanthus, chiefly by means of 

 intra-vitam staining with methylene blue. The sense cells in the epidermis 

 end in a sense hair or in a thick, stiff bristle (the latter especially in the sto- 

 modaeum of B.) situated on a conspicuous bulb which is level with the surface 

 of the epithelium. In the stomodseum of B. the sense cell often ends in an 

 elongate ellipse, which lies parallel to the surface, and from which the sense 

 hair issues. The sense cells of the pedal disc of B. are elongate, slender, 

 varicose filaments; similar ones are found, but rarely, in the tentacles; in the 

 rest of the ectoderm the sense cells are more massive. The sense cells in the 

 endoderm are shorter and stouter. Anastomoses between the nerve fibres of 

 sense cells were observed only very rarely, nor were connections seen between 

 them and a subepithelial nervous network. Fusiform, triangular or ovoid 

 ganglion cells, each with 3 (or 2) equivalent nerve fibres are present. There 

 seem to be two types of ganglion cells - - (1) those whose processes cover the 

 greatest area and do not run in any definite direction, bipolar cells of this 

 type are rare; (2) those whose processes run in a definite direction, usually 

 bipolar cells. The first type is found in the nerve centre of the stomodseum, 

 the second in the most pronounced nerve tracts, namely, those along the sipho- 

 noglyph of B. On the tentacles and in the stomodseum of B. there are cells 

 which externally resemble sense cells. Near the nucleus of the cell there is 

 a nematocyst which, according to its stage of development, is small and 

 completely covered with a thick layer of protoplasm or is large and has only 

 a thin enveloping film of protoplasm. Before the formation of the nematocyst 

 such a cell is indistinguishable from a sense cell and is able to function as 

 such. A connection between the nervous system and the gland cells was not 

 observed. In the ectoderm of the tentacle and of the upper part of the sto- 

 modseum of B. there are very long filiform, varicose cells, the long proximal 

 processes of which terminate on the muscle fibres in an elongate foot-like 

 ending, the direction of which coincides with that of the muscle fibres. These 

 cells have a close similarity to nerve cells but the author regards them as 

 Stiitzzellen. In well differentiated preparations of the red area [s. below 

 above the stomodseum of B. cells are seen in which there is a smooth dark 

 fibre which runs in a spiral manner from the base of the cell to near the 

 nucleus ; it is seen again in the distal dilatation of the sense cell. This fibre 

 may be thicker than the nerve fibre which issues from the cell; so it probably 

 represents a bundle of neurofibrillse which have become massed together 

 during preparation. Sense cells are almost evenly distributed over the whole 

 of the tentacle and are not specially abundant at its tip as stated by the 

 Hertwigs. No other portion (except the stomodseum) equals the tentacles in 

 regard to the number of sense cells present. Most of the sense cells in the 

 tentacles of Cerianthus are unipolar and send their processes towards the base 

 of the tentacle, in B. there are bipolar cells as well, the processes of the 

 latter, especially the stronger one, also run parallel to the axis of tentacle. 

 The sense cells of the body wall are more widely spaced, their processes 

 generally run parallel to the long axis of the body. Numerous sense cells 

 and sporadic ganglion cells are present in the oral disc of B. and Act. equina, 

 no definite arrangement of their fibres was ascertained except near the mouth 

 where they are radial. Ganglion cells were not found in the external ecto- 

 derm, except in the oral disc. The stomodseum is more richly supplied with 



