ME. A. W, WATERS ON MBMBEANIPORIDiE. 659 



position, while the pores within the chamber must be compared 

 with the communication pores o£ the rosette-plates. The occur- 

 rence of these interzocecial chambers should always be mentioned, 

 but it does not seem as though any wide generalizations can be 

 based upon the fact of the connection being direct or through a 

 chamber. This indirect method of communication is found in 

 many of the higher Chilostomata, and will subsequently be 

 dealt with. I described and figured these pore-chambers in 

 Gribrilina crihrosa^, and on account of these chambers Jullien 

 made this the type of a new genus Collarina, although they 

 occur in many Cribrilinae. Memlraniporella, and in a large 

 number of Chilostomata. 



Smitt also figures the pore-chamber in M. trifolium^ Wood, and 

 refers to it in this species and in M. lineata, L. 



In many cases the most convenient method is to boil in caustic 

 potash, well wash, and boil in water to prevent further change 

 taking place ; and in this way incrusting forms are frequently 

 separated from the seaweed and shells upon which they grow, 

 and the interior can be examined, besides which the calcareous 

 and purely chitinous parts can be more readily studied. 



Levinsen f, as his definition of the group A of the Memhrani- 

 por<s, says " forbindelspladerne " (rosette-plates) do not show 

 through upon the underside of the colony, and do not form 

 curved lines within the border in the front part of the individual 

 zocecia. These chambers can well be seen in M. lineata (PI. 48. 

 fig. 9), and here there are acute spines within the chambers which 

 he calls " tandformede forlaengelse." 



The lateral rosette-plates are found in several creeping forms, 

 and may here be of determinative value, as seen in various genera ; 

 among others Pyripora and creeping M. inarmata. 



In the distal wall there may be only one rosette-plate, as in 

 M, corhtola, pyrula, papulifera, patellaria, tenuirostris, acuta, 

 argentea, crassimarginata, falcifera, inarmata, minax, perfragilis, 

 radicifera, Sosselii, solidula, valdemunita, cristata var. hilaminata, 

 elliptica, pilosa, onaderensis, Lacroiocii, aurita, sejuncta, umhonata, 

 granulifera, angtdosa. 



Or two, as in M. membranacea, nitens, C. acantliina, cervicornis, 

 capensis, M. danica, imhellis, gregaria, 



* Ann. & Mag. Nat. Hist. ser. 5, vol. iii. p. 36, pi. ix. fig. 4. 

 t Danske Dyr, p. 53. 



