TERMINOLOGY 



523 



XIX 



I 



fresh-water and marine Polyzoa. The use of formaline (see p. 

 229) may be strongly recommended for the Vesicularina. 



The only recent work dealing with all the marine British 

 forms is Mr. Hincks' invaluable History of the British Marine 

 Polyzoa} As the use of this book, unaided by any artificial 

 help, is by no means easy to the beginner, the following key has 

 been compiled as an index to the genera. The Entoproct forms, 

 Loxosoma and Pedicellina (see pp. 488-491), are not included in 

 the table. 



In order to facilitate the use of the table here given in eon- 



Fig. 256. Illustrating 

 the terminology of 

 the front surface of 

 the zooecium (Cheilo- 

 stomata). A, Mem- 

 hranipora (Electro) 

 pUosa L., Cromer, x 

 47 ; ap,th(i membran- 

 ous " aperture ; " <>, 

 orifice. B, Memfo-ani- 

 />i>ro * flemingii Busk, 

 Plymouth, x 60 ; op, 

 the aperture, enclosed 

 in a calcareous 

 "area" (a); a?;,avicu- 

 larium ; s, marginal 

 spines. C, Mi cropo ru 

 coriacea Esper, Ply- 

 mouth, x 43 ; a, area 

 (calcareous) ; o, oper- 

 culum ; ov, ovicell. 



junction with Mr. Hincks' work, the nomenclature there adopted 

 has been followed throughout. Eeferences to other descriptions 

 of the species may be obtained by consulting Miss Jelly's admir- 

 able Synonymic Catalogue of the Recent Marine Bryozoa'r 



Terminology. A few technical terms must of necessity be 

 employed. The colony is adherent when its zooecia are attached 

 to the object on which the colony is growing. The zooecium is 

 the body- wall of a single individual ; and, except in transparent 

 species, is the only part which can be seen from the outside in 

 the retracted condition of the polypide or tentacles with the 

 alimentary canal. The outermost layer of the zooecium is known 

 as the ectocyst ; it may be simply membranous, or Calcified, or 

 may be rendered opaque by foreign bodies ; its surface in 



1 Two vols. 8vo. London (Van Voorst), 1880. 

 2 8vo. London (Dulau), 1889. 



