PLATE 5.— Unicellular Algae, etc. 



Figure 



1. Hydrocytium acuminatum, a, young plant ; b, more advanced ; c, older stage, with 



the gonidia divided ; d, cell about to burst ; e, cell burst and discharging zoospores. 



2. Characium Sieboldii. a, b, c, successive stages of young plant ; d, mature cell dis- 



charging its zoospores. 



3. Sciadium arbuscula. a, young plants, the right-hand "one setting free the gonidia of 



the second generation ; b, an older plant with an umbel of secondary cells, some 

 discharging their gonidia of the third generation ; c, part of an umbel of cells from 

 the last generation of a family, the gonidia being discharged as free zoospores. 



4. CMorospJuera Oliveri. a, perfect plant ; b, a plant dividing into two ; c, the same with 



the two new cells discharged from the parent. 



5. Apioeystis Brauniana. a, perfect plant ; b, zoospore ; c, germinating plant from a 



zoospore. 



6. Codiolum gregarium. a, young plant ; b, nearly mature. 



7. Chytridium OUa upon an (Edogonium. a, a, Chytridia burst and discharging their 



zoospores ; b, a cell not yet open. 



8. Pythium entophytum on CMorosphaera. a, group, partly mature ; b, side view of a 



single cell perforating the cell-wall of the CMorospJuera, and with its neck opened, 

 discharging the contents. 



9. Clathrocystis ceruginosa. a, b, c, fronds in successive stages of growth, the natural 



colour ; d, a frond dried ; e, highly magnified fragment, showing the minute cells 

 imbedded in the gelatinous frond. 



10. Pandorina Morum. a, side view of active form with sixteen gonidia ; b, side view of 



larger form with thirty -two gonidia ; c, end view of a ; d, form with crowded 

 gonidia after fertilization, the cilia lost ; e, the same more advanced, having lost the 

 gelatinous common envelope, and the cell-contents red ; /, a single encysted goni- 

 diuni (resting-spore) from e, more magnified ; g, side view of a gonidium with the 

 contents becoming converted into spermatozoids ; h, a single spermatozoid. 



11. Ophiocytium majus, in different stages of development. 



12. Spore-formation of Vaucheria sessilis. A, the sporange s, and the antheridium a, not 



yet open ; B, both open, the epoch of fertilization ; C, decaying filament with ripe 

 spore. 



13. Fragment of a filament of (Edogonium tumidulum, consisting of antheridial cells, one 



discharging a spermatozoid. 



14. Fragment of (E. ciliatum, consisting of parent cells of androspores, one of which is 



escaping. 



15. Fragment of (E. gemelliparum, male plant, consisting of antheridial cells, some bursting 



to discharge their twin spermatozoids. 



16. Sporange with sessile dwarf male plant of (E. ciliatum. 



17. The same older, the dwarf male plant a having burst and discharged the spermato- 



zoid which has entered the sporangial cell or oogonium. 



18. Spermatozoids of (E. ciliatum. 



19. A dwarf male plant of (E. ciliatum, discharging an androspore from its large basal cell. 



20. Filament of (E. Braunii. a, a, dwarf male plants, sessile on the filament ; b, b, ferti- 



lized spores in the sporangial cells. 



21. Ripe spore of (E. ciliatum. 



22. Gemmation of the resting-spore of Bulboehcete intermedia, a, ripe spore ; b, the same 



enlarged ; c, the contents dividing ; d, the contents converted into four ciliated 

 zoospores. 



