96 VIGNETTES FROM INVISIBLE LIFE, 



creature's nourishment. These plumes are en- 

 dowed with great sensibility and under perfect 

 control ; so that on the least alarm they are 

 rapidly withdrawn, and with returning sense of 

 security are again slowly protruded, folded as 

 in a bundle, and presently expanding in all 

 their glory, resume the normal activities of their 

 being. 



The general plan of organisation is much alike 

 in all the Polyzoa. A tubular ciliated canal " bent 

 back on itself " is suspended in a transparent mem- 

 branous sac, to which it is connected. It is sur- 

 mounted with the plume or crown of tentacles before 

 named, forming the head and mouth and receiving 

 the food, is endowed with all the functions of diges- 

 tion and assimilation. The enveloping sac is filled 

 with fluid matter, and furnished with nerves, muscles, 

 and reproductive functions. It also secretes another 

 membrane of greater strength on its exterior, form- 

 ing a double protection to the delicate life within 

 its folds. 



It has several methods of reproduction, one of 

 which is so intimately blended with its organisation 

 that this seems the fitting place to mention it. This 



