EXPLANATION OF PLATE XXIH. 

 Fig. 

 1-2. Synura m'ELLA, Ehr., vol. i. p. 412 (Stein). — i, Adult spheroidal colony-stock, 



composed of animalcules possessing no eye-like pigment-specks, x 350 ; 



2, smaller colony of variety having two anterior eye-like pigment-specks. 



3. SVNCRYPTA VOLVOX, Ehr., vol. i. p. 413, X 200 (Stein). 



4-15. Uroglena VOLVOX, Ehr., vol. i. p. 414. — 4, Subspheroidal colony-stock, x 150 ; 

 5, segment of a similar colony, more highly magnified, containing sporular 

 elements in various phases of development ; 6, a single animalcule ; e, eye- 

 like pigment-speck; cv, contractile vesicle; am, refringent amylaceous 

 corpuscle; 7 and 8, isolated spores, x 1200; encysted zooid, with body- 

 mass divided by segmentation into four sporular elements; 10 and 11, 

 sporocysts fractured by artificial pressure, and hberating their contained 

 sporular elements, x 400 ; 12, animalcule as represented by Stein ; 13, three 

 zooids of the same species, after Biitschli ; 14-15, examples treated with 

 acetic acid and carmine, after Biitschli and Stein. 



16. Synura (Uvella) fimbriat.^, From, sp., x 400 (De Fromentel). 



17-30. Stylobryon petiolatum, Duj. sp., vol. i. p. 278. — 17, Colony-stock of six 

 zooids, as observed by the author, having very- long, slender pedicles to their 

 loricse, x 400 ; 18, colony-stock, in which the pedicles of the distal series 

 are rudimentarily developed ; 19 and 20, animalcules in dorsal and profile 

 view, as examined in living state, x 800; 21-23, example from another 

 ^ colony preser%'ed with osmic acid, the longer flagellum being variously 

 convoluted ; 24 and 25, examples with entire body-substance separated into 

 sporular elements; 26, isolated spores, x 1200; 27 and 28, colony-stocks 

 of the same type, after Stein ; 29 and 30, colony-stock and isolated animalcule 

 of the same species, as figured and described by De Fromentel under the 

 title of Stylobryon insignis. 



