1900] MICROSCOPICAL JOURNAL. 213 



times. This is Stylodictya. There is another formed by 

 crystal hexagons united in two spheres open below and 

 closed above and ending on a spine. This is Encyrtidium, 

 but they may appear almost endless in form. They are 

 not marked so finely as the Bacillaria, in fact they are not 

 so small, but they are as beautiful in form. Hseckel clas- 

 sifies them as follows : 



1. Spumellaria. — Capsular membrane perforated by 

 innumerable fine pores. Fundamental form originally 

 spherical, skeleton silicious or in some cases absent. No 

 dark pigment-body (phaeodium) in the extra-capsular sar- 

 code. 



2. Acantharia. — Capsular membrane perforated by 

 numerous fine pores, fundamental form originally spher- 

 ical. Skeleton composed of "acanthine." No dark pig- 

 ment body in the extra-capsular sarcode. 



3. Nascellaria. — Capsular membrane perforated by 

 a porous area or by one single large opening divided into 

 numerous very fine pores. Fundamental form originally 

 egg-shaped. Skeleton siliceous. No dark pigment-body 

 (phaeodium) in the extra-capsular sarcode. 



4. Ph(ED0ria. — Capsularmembrane double, perforated 

 by a simple main opening prolonged into a tube, com- 

 monly with one or two small accessory openings. Fun- 

 damental form originally egg-shaped. A dark pigment- 

 body (phaeodium) is constantly present in the extra-cap- 

 sular sarcode. The skeleton is silicious, being usually 

 composed of a compound of silica with some organic sub- 

 stance, but in other instances (Dictyocha) consisting of 

 pure silica. 



It will be necessary to say here something about the 

 form known as Dictyocha. When searching the rocks that 

 make up the Oligocene tertiary and also, more rarely, ex- 

 amining the sea-mud that comes from the deep waters of 

 the ocean, the observer comes across certain strange ob- 

 jects, siliceous in chemical composition and microscopic in 



