XVI INTRODUCTION. 



or altogether absent, and only reappear with the return of 

 spring. This condition may remind us the of winter rest 

 of the plant. 



Besides the polypites, which are essential parts of 

 every zoophyte, special appendages of the ccenosarc are 

 met with in some species. Amongst these must be placed 

 the curious structures which have been named "nema- 

 tophores" by Mr. Busk, and which are characteristic of 

 the family PlumulariidfS . They consist of an extension of 

 the polypary, which may be tubular, or cup-shaped, or 

 conical, open at the upper extremity, and enclosing a 

 granular mass, in which large thread-cells are sometimes 

 imbedded. They may be classified as simple or compound, 

 sessile or pedunculate. The simple nematophore is a 

 chitiiious tube or cup, consisting of a single chamber. The 

 compound nematophore is bithalamic, having a slender 

 tubular portion below (Woodcut, fig. v. a) , and expanding 

 above into a hemispherical cup (Woodcut, fig. v. b). It is 

 attached at the base only, and free throughout its length ; 

 whereas the simple nematophore is generally to a consider- 

 able extent adnate to the calycle or stem. 



The pedunculate form (Woodcut, fig. v.) I have only met 

 with on Plumularia Catharina. In this -p- 



species the pair of lateral nematophores 

 connected with the calycle are mounted 

 on peduncles, by which they are raised 

 to about the level of the rim. They are 

 of the bithalamic type. The other ne- 

 matophores, which are profusely distri- 

 buted over this beautiful species, are sessile. 



Good examples of the simple tubular form are afforded 

 by Aglaophenia phima (Woodcut, fig. vi.) and A. tubvlifera. 



