NO. 1 OSBURN : EASTERN PACIFIC BRYOZOA CHEILOSTOMATA 9 



Communication pores. For physiological communication between ad- 

 jacent individuals there are minute pores in the lateral and distal walls. 

 These are of three kinds: 1. uniporous septulae which are arranged in a 

 row or scattered ; 2. multiporous septulae, in which case the pores are 

 aggregated in small rounded areas known as "rosette plates ;" 3. dietellae 

 or "pore chambers," which are in the form of small cavities at the base 

 of the vertical walls and within which the pores are located. 



Polymorphism. This a common feature of this group and various 

 names have been given to the different types of individuals: 1. autozooecia 

 to the ordinary nutritive members of the colony ; 2. gonozooecia to those 

 specially modified for reproduction ; 3. heterozooecia and kenozooecia to 

 those modified for other functions of the colony (see glossary). 



Ovicells. Ooecia or ovicells are usually present, though in some cases 

 the eggs develop to the swimming larval stage within the zooecial cavity. 

 Endozooecial ovicells are internal extensions of the distal wall to form 

 small chambers, with the opening below the operculum ; usually they are 

 inconspicuous, but may be quite evident externally. Hyperstomial ovi- 

 cells are developed above and distal to the aperture, usually reposing on 

 the base of the next zooecium, and the orifice opens above the distal 

 zooecial wall. 



Avicularia and vibracula. These are highly modified and usually much 

 reduced individuals of special function, serving as zooecial or colonial 

 organs (see glossary). 



Levinsen ( 1909) subdivided the Cheilostomata into the Anasca, which 

 have a membranous frontal area and no compensatrix, and the Ascophora 

 which have a rigid frontal area and in which the compensatrix regulates 

 the internal water pressure. 



ANASCA Levinsen, 1909 



Levinsen (1909:91) defined the "Suborder Anasca" as follows: "A 

 compensation sac is wanting, and the front wall is either wholly or in 

 part membranaceous, or calcareous, depressed and surrounded by raised 

 margins. In the heterozooecia the opercular and the subopercular areas 

 are as a rule not separated by a continuous calcareous bar, but only 

 partially by the hinge-teeth of the operculum." At the same time he set 

 up three divisions: Malacostega, Coilostega and Pseudostega. 



The Malacostega, Division I, was defined, "The individual zooecia 

 are plainly marked off on the surface of the colony. The frontal wall 

 quite or partially uncalcified and the operculum as a rule a membranous 

 valve, the rim of which is chitinized, but which proximally passes over 



