584 Canon A. M. Norman — Xotes on the 



" Membranipora." 



The so-called genus Membranipora contains a lietero- 

 geneous assemblage of forms ■wliicli only agree in these 

 particulars — namely^ that a larger or smaller portion of the 

 front ^-all consists of a membranous covering, and that the 

 oral opening is generally of the simplest character in the 

 anterior part of this membrane. It has always been a 

 matter of surprise to me that, though Hincks removed two 

 or three species to other genera, he left such a strange 

 assemblage of forms to be associated with Memhranipora 

 memhranacea. The explanation is, 1 suppose, that he relied 

 almost entirely on the oral opening for the establishment of 

 his genera. I cannot but think that in dividing this group 

 use should be made of the presence or absence of the 

 ooscium, for the mode of reproduction must be of more 

 importance than most other characters. The character of the 

 ooecium when present, and the partial or entire membranous 

 epitheca, must be considered. The absence or presence of 

 avicularia, their character, whether occupying a separate 

 chamber or belonging to the zooecium, their position and 

 structure are more or less valuable according to other 

 characters -which accompany these differences. Mr. Waters, 

 Herr Le\dnsen, and others have devoted much time and 

 labour to the examination of the pore-chambers and rosettes : 

 the former has summarized his obser^•ations in his paper 

 '' Observations on the Membraniporidae,'^ Journ. Linn. Soc, 

 Zool. vol. xxvi. 1898, p. 654; and Herr Levinsen has given 

 figures of the pore-chambers of several species in his excel- 

 lent 'Zoologica Danica, ]\Iosdyr/ 1894. In the preparation 

 of this paper I have examined almost every northern species 

 with respect to the pore-chambers, and have found them to 

 be very valuable as generic characters. They are often very 

 easily seen ; but in some cases, though they exist in the 

 walls of the zooecia, they do not project beyond them and are 

 then often very difficult to determine with certainty. I have 

 used three methods in their examination : first, incineration ; 

 secondly, boiling in liquor potasspe; thirdly, placing in Eau 

 de Javille. The use of the latter destroys not only the soft 

 tissues but dissolves chitine, so that it must not be used when 

 it is desired to observe the opercula. 



I have illustrated the pore-chambers of several species, 

 but have purposely omitted drawings of those species which 

 Levinsen has already figured, unless the species is the type 

 of a genus as here instituted. 



I may mention two little matters which have struck me 

 as interesting in my investigations : — 



