MICROPORELLA. 205 



nitfly shaped opening in the front wall of the cell, which 

 belongs to this genus. But the character, which is con- 

 stant, may fairly be accounted of considerable importance, 

 and, taken in combination with the form of the aperture, 

 is a good diagnostic mark. 



Milne-Edwards has suggested that the pores may be 

 connected with the function of respiration. In his ac- 

 count of Eschara gracilis, Lamk.* (a species probably 

 referable to the next family), he expresses his belief that 

 the surrounding water may find access through these 

 openings to the perivisceral cavity, and so promote the 

 oxygenization of the fluids. Whatever may be thought 

 of this view, it is in the highest degree probable that these 

 structures bear some not unimportant relation to the 

 vital economy, and are fairly entitled to consideration in 

 a natural system. In the large and very beautiful pore 

 of M. Malusii (woodcut, fig. 8) the aperture is guarded 

 by numerous delicate teeth, which are set round its inner 

 edge ; through these the water in all probability finds its 

 way to the interior of the cell. In this case 

 the dentate opening must act as a sieve or 

 strainer, and prevent the entrance of bodies 

 that, from their size or otherwise, might be 

 a source of injury or inconvenience to the Median pore. 

 polypide. 



D'Orbignjr's Reptoporina includes the present group; 

 but it also embraces a somewhat miscellaneous assem- 

 blage of forms ; and I have therefore thought it better 

 (though most desirous to avoid additions to the nomen- 

 clature) to designate it by a new name. Lepralia bicrig- 

 /a/a, Busk (Cape Horn), and L. Califomica, id., belong 

 to this genus. The latter has an avicularium on each 



* ' Recherche* anatomiquea, physiologiquea et soologiquea ur le 

 Polype*' (1838) : " Sur les Ewharen," p. 30. 



