INTRODUCTION. X11L 



Besides the ordinary tentacles, peculiar appendages occur 

 in two genera, Cladonema (Plate XI. fig. 2) and Stauri- 

 dium (Plate XII. fig. 1), which I have named false tenta- 

 cles, and which seem to discharge the function of tactile 

 organs. They are filiform processes, standing out in a 

 single series, near the base of the body at some distance 

 below the arms, and at first sight might be taken for ten- 

 tacles deprived of their capitate extremities. They are, 

 however, perfectly rigid, and the tips at least are thickly 

 covered with the sensitive palpocils. It seems to be their 

 office to warn the polypite of the presence of prey, for if 

 one of them is touched by an animalcule in its course, the 

 body is immediately bent towards it, and the tentacles are 

 brought into play. 



In a few species the tentacles are united for a portion of 

 their length by a very delicate membranous web. In 

 Ophiodes (Plate XLV. fig. 2b) it is well developed, and 

 forms a rather deep cup enclosing the proboscis. In this 

 genus it is armed with small clusters of thread-cells, which 

 are set round it, one in each of the spaces between the 

 tentacles, like so many batteries, and can discharge on the 

 shortest notice a multitude of poisoned darts. It is very 

 interesting to see the threads cast forth beyond the tips of 

 the tentacles, and waving about in all directions amongst 

 them, as if prepared to act with them in seizing and dis- 

 abling their prey. 



The intertentacular web is of rare occurrence, and is 

 generally very slightly developed ; but it has a special 

 interest as the homologue in the polypite of the swimming- 

 bell in the free sexual zooid. 



Amongst the Thecaphora the polypite is protected by a 

 calycle (Woodcut, fig. i.), within which it shelters itself by 



