POLYTRIOHUM. 



[ 625 ] 



POLYZOA. 



cence, composed of scale-like leaves and 

 paraphyses surrounding a number of subu- 

 late sacs constituting the antheridia. The 

 male flowers of P. commune tfuwiperinum, &c. 



Fig. 600. 



Fig. 601. 



Polytrichum commune. 



Capsule with operculum. Section of young capsule 

 Magnified 10 diameters. 



showing the plaited spo- 

 rangial membrane. 



are found everywhere on heaths in spring. 

 The antheridia may be readily extracted un- 

 der a simple lens, and, when placed in water 



Fig. 602. 



Fig. 603. 



Polytrichum commune. 



Fragment of peristome. Columella with section 



Magn. 100 diams. of tne apophysis. 



Magn. 25 diams. 



under the compound microscope, soon (if 

 ripe) burst at the summit and dis charge the 

 spermatozoids ; these usually escape still 

 enclosed in their parent cells, which when 

 first discharged cohere in a gelatinous mass ; 

 but the ciliated spermatozoids (PI. 40. fig. 

 33) escape and swim actively in the water. 



They require at least an eighth object-glass 

 for examination ; and the cilia are seen most 

 clearly after drying the object, or treating 

 it with tincture of iodine. 



Fig. 604. 



Fig. 605. 



Polytrichum commune. 



Male inflorescence. Innovation from male 



One half nat. size. inflorescence. 



Magn. 5 diams. 



BIBL. Wilson, Bryol Brit. p. 205 et sea. : 

 Thuret, Ann. Sc. Nat. 3. xvi. 26. pi. 14. 



POLYZO'A or BRYOZOA. A class of 

 Animals, belonging to the subkingdom 

 Mollusca. 



Char. Polypif orm, aggregate ; individual 

 bodies microscopic, contained in horny or 

 calcareous cells, often connected by tubular 

 stems, forming a usually branched zoary ; 

 mouth surrounded by long, ciliated, uncon- 

 tractile tentacles ; mouth and anus separate, 

 but near each other. Marine and fresh- 

 water. 



They are found everywhere on the sea- 

 shore, either rooted to, or forming a crust 

 upon submerged rocks, stones, shells, &c. 

 The individual is called a polypide ; and 

 the aggregate or colony constitutes a 

 ccencecium or polyzoarium ; it is usually 

 of a whitish or brownish colour, of a 

 horny or calcareous texture, and consists 

 either of cells or cups simply aggregated 

 (PL 41. figs. 17, 20), or connected by tubu- 

 lar stems, and often arranged in elegant 

 plant-like forms (PI. 41. fig. 5 a). The 

 stems are divided into compartments by 

 perforated septa (PI. 41. fig. 5 /), through 

 which thread-like filaments of the sarcode 



2s 



