1 1 



\ frustule of Campy 'lodiscus, as stated, is formed by two 

 saddle-shaped wives, these saddles being thrown across one 

 another with their concave sides facing but not touching 



other, so as to leave space for the soft, living contents of the 

 diatom. The connective zones, as mother diatoms, telescope 



one in the other, and unite the two valves by their outer mar 

 gins. Having to follow the curvatures of two valves bent in 

 opposite directions, they thereby acquire a remarkable zig zag 

 or undulating appearance, which at fust sight is often som< what 

 difficult of interpretation, especially when complicated with the 

 re-duplication of the cells. 



All the other characteristics of the genus are those of the 

 family ' { Surirella,'' to which it clearly belongs, although in some 

 forms of Campylodiscus the marginal wings seem to be obsolete 

 or wanting, or turned upwards in such a manner as to obliterate 

 them apparently from a side-view aspect. 



The endochrome or coloured contents, as seen in the living 

 diatom, places the Campylodisci among the Placochromaticaz of 

 Pfitzer's and Petit's classifications, which comprise such Diatoms 

 as have in life and health their endochrome forming lamellar 

 plates or chromatophores, in contradistinction to the Coccochro- 

 matica\ which have a granular endochrome. In Campylodiscus 

 two layers of endochrome exist in each frustule. one applied to 

 the inner surface of each of the valves. The re-duplication of 

 the frustules, or vegetative cells, takes place in the ordinary 

 way. Nothing is known relating to the formation of Auxo- 

 spores or germs in the Campylodisci. 



All Campylodisci, with the exception of one or two species. 

 are marine or from brackish water. The majority of forms are 

 tropical, although a few reach both the Arctic and Antarctic 

 Seas. From the Air north, Prof. Cleve has registered the 

 following seven forms : — 



Campylodiscus annularis. Campylodiscus clypens. 



,, grosnlqndicus. „ Tluo ctii and varie- 



,, echeneis. ,, Hybernicus. [ties. 



,, biangulatus = Lor en zi anus. 



