EXPLANATION OF PLATES I-XIV 



The scale of the figures is indicated on each plate, and is further explained in the legend, 

 in each case. The plane of the sections and the nomenclature of the surfaces are described in 

 accordance with the text-figure on p. 23; a section transverse to the actual principal axis of the 

 zooid being regarded as "frontal", while a "transverse" section is parallel to that plane. The 

 terms "right" and "left" are used for descriptive purposes, and do not necessarily corre.spond 

 with the actual right and left sides of the original specimens. Certain details are omitted in 

 some of the figures : thus the nerve-layer of the epidermis is only shewn when it is unmistakeably 

 present; while many of the strands which traverse the collar-cavities are omitted. 



