XXXV111 INTRODUCTION. 



The whole system of cords now described, with its 

 globular enlargements at the junction of the zooecia with 

 the stem, and of one compartment of the stem with 

 another, and its filamentary offshoots, exhibits the same 

 essential structure, and must be regarded as composed of 

 one and the same tissue. Its histological character has 

 been studied by Nitsche, Reichert, and Joliet, but most 



Fig. xvi. 



t'elle of the Eiulosarc. 



exhaustively by the latter writer. It is composed in 

 great measure of minutely granular fusiform cells, either 

 with or without a distinct nucleus, attenuated and pointed 

 at the two extremities, and somewhat swollen in the centre, 

 which are disposed longitudinally in the tissue. (Woodcut, 

 fig. xvi.) . In some cases the cord is laden with refringent 

 granules, which are so crowded as almost to conceal it. 



The plan of the endosarc (to adopt Joliet's name for 

 this tissue) varies somewhat in the different divisions 

 of the class. Amongst the Chetfustomala (for instance), 



