EXPLANATION OF PLATE XXI. (continued). 

 FIG. 



30-32. COLACIUM CALVUM, St., vol. i. p. 395 (Stein). 30, Social colony-stock, x 400 ; 

 31 and 32, detached, free-swimming animalcules in extended and contracted 

 states. 



33. COLACIUM ARBUSCULA, St., vol. i. p. 394. Tree-like colony-stock, x 500 (Stein). 



34-38. COLACIUM VESICULOSUM, Ehr.. vol. i. p. 395 (Stein). 34, Sedentary colony-stock, 

 X 600 ; 35, detached, free-swimming animalcule ; 36-38, successive de- 

 velopmental phases following on the attachment of a motile zooid, and 

 resulting, through further subdivision, in the building up of a more or less 

 extensive sedentary stock. 



39-41. COLACIUM STEINII, S. K., vol. i. p. 395. 39, Erect colony-stock, x 350; 

 40, arborescent stock, x 700, showing variety of contracted or contorted 

 forms assumed at will by the component animalcules ; 41, animalcule in an 

 encysted state, with the body-contents divided into sporular elements. 



42. CRYPTOGLENA CONICA, Ehr., vol. i. p. 419, x 500 (Ehrenberg). 



43-45. CRYPTOGLENA ANGULOSA, Carter, vol. i. p. 420 (Carter). 43, Normal aspect ; 



44, example enclosing four endogenously developed germinal bodies ; 



45, lateral aspect, x 500. 



46-51. DISTIGMA PROTEUS, Ehr., vol. i. p. 418 (Stein). 46, Normal biflagellate ani- 

 malcule, x 500 ; 47 and 48, old, non-flagellate, and repent zooids (Proteus 

 tenax, O. F. Miiller ?) ; 49 and 50, young free-swimming animalcules; 51, 

 still younger monoflagellate example (Monas punctum, Ehr.). 



52, 53. ZYGOSELMIS NEBULOSA, Duj., vol. i. p. 417 (Stein), x 1000. 53, Example with 

 body distended by ingested diatoms. 



54-59. EUTREPTIA VIRIDIS, Pty., vol. i. p. 416. 54 and 55, Normal free-swimming 

 animalcules, X 250 ; 56, repent example ; 57, sporocyst burst and liberating 

 green amcebiform germs, x 400 ; 58, amcebiform germs more highly mag- 

 nified ; 59, young monoflagellate zooids, x 250. 



