BY R. VON LENDENFELD, PH.D. 561 



their shape they resemble those elements of other sponges and 

 higher coelenterates very closely which are considered as sensitive 

 elements. The nucleus is different from the nucleus of the gland 

 cell. It is oval and slightly smaller, 0-0038 mm. long and 

 O'OOS mm. broad. The slender distal portion of the cell seems to 

 project slightly beyond the surface. (Fig. 5.) In the centre the cell is 

 barely thicker than the nucleus. Proximallj' it extends to form a 

 process in the shape of a very fine granular thread. This becomes 

 more and more indistinct the further we follow it down. I have, 

 however, traced it to a distance of 0'03 mm. from the nucleus. 



In the parts of the membrane, distant from the pores, amaeboid 

 wandering cells (fig. 5 a), and tangental muscular cells arc found 

 (fig. 5 m.) The latter extend in every direction and are always 

 spindle-shaped. 



The greatest interest attaches to the cells (fig. 5 g), which 

 constitute the ring visible already with a low magnifying power. 



The nuclei of these cells are regularly spherical and larger than 

 the nuclei of the amceboid wandering cells measuring 0004 mm., 

 in diameter. The body of the cell is irregularly bulbous and 

 extends in the shape of fine processes in every direction. It appears 

 that some of these processes connect these cells with the spindle- 

 shaped sensitive cells described above, they appear as nerve fibres. 

 The cells themselves are situated very close together and their 

 processes often touch. I consider them as ganglia cells, and the 

 whole structure as a circular nerve or ganglion surrounding the 

 pore 



Although the nuclei become very clearly visible after staining 

 the protoplasmatic body of the cell always remains more or less 

 indistinct, so that particularly the processes and outlines of the 

 ganglia cells cannot be described with great accuracy. 



It appears that changes in the water are perceived by the 

 sensitive and ganglia cells round the pores, and that the latter 

 under circumstances incite the muscular cells in the membrane to 

 contract, whereby the diameter of the pore may be changed. 



