EXPLANATION OF PLATE I. 

 FIG. 



i, 2. TRYPANOSOMA SANGUINIS, Grube, x 600 (Ray Lankester). 

 3-6. TRYPANOSOMA EBERTHI, S. K., x 1200 (Eberth). 

 7, 8. ACTINOMONAS PUSILLA, S. K. 7, Zooid attached by a single stalk-like filament ; 



8, zooid attached by a number of its ray-like pseudopodia, x 800. 

 9-11. ACTINOPHRYS SOL, Ehr. Successive developmental phases out of a primary 



monadiform germ, as observed by the author, x 600. 



12-17. MAGOSPH^ERA PLANULA, Hkl. 12, Adult spheroidal colony-stock, x 240; 13, 

 ideal optical section of the same ; 14, a single isolated zooid derived from the 

 disintegration of the social colony-stock ; 15, a similar zooid having assumed 

 an amoeboid phase ; 16 and 17, encysted zooids, the one at 17 having divided 

 by segmentation into four spheroidal sporular bodies (Haeckel). 

 18. ACTINOMONAS MIRABILIS, S. K., x 800. 

 19, 20. MASTIGAMCEBA RAMULOSA, S. K., extended and contracted conditions, x 400. 



21. MASTIGAMCEBA ASPERA, Sclz., x 170 (Schulze). 

 22, 23. MASTIGAMCEBA MONOCILIATA, Carter sp., dimensions unrecorded (Carter). 



24. EUCHITONIA VIRCHOWII, Hkl., x 370 (Haeckel). 



25. SPONGOCYCLIA CHARYBDEA, Hkl., x 72 (Haeckel). 



26, 27. RHIZOMONAS VERRUCOSA, S. K. 26, Animalcule enclosed within granular 

 gelatinous sheath, X 750 ; 27, example devoid of such covering. 



28, 29. PODOSTOMA FILIGERUM, C. & L. 28, Animalcule with flagelliferous pseudo- 

 podia extended ; 29, example with appendages entirely retracted, x 250 

 (Clap, and Lach.). 



30. MASTIGAMCEBA SIMPLEX, S. K. Having attached by a posteriorly extended 

 thread of sarcode the frustule of a diatom, probably ejected from its body, 

 X 800. 



31-33. REPTOMONAS CAUDATA, S. K. 31, Normal animalcule, profile view, x 800; 



32, Dorsal view of example with short posterior pseudopodal extensions ; 



33, a similar example in the act of ingesting food by the peripheral exten- 

 sion of its body-sarcode. 



34-44. NOCTILUCA MILIARIS, Suriray. 34, Normal adult animalcule, X 40; 35 and 

 36, peripheral regions of two animalcules having variously developed masses 

 of germinal bodies, x 50 (Cienkowski) ; 37, a similar germinal patch more 

 highly magnified, and showing its composition of uniflagellate monadiform 

 elements (Cienk.) ; 38-40, isolated monadiform germs in different aspects and 

 phases of development, X 500 (Cienk.) ; 41, more abnormal zoospore-like 

 germ, x 500 (Cienk.) ; 42, entire adult animalcule, dorsal view, showing 

 median groove, stylate rod, and tooth-like process (Huxley) ; 43, latero- 

 inferior view, showing oral cavity with tooth-like process and contained 

 cilium (Huxley) ; 44, conjugation of two animalcules (Cienk.). 



45. Encysted condition of Noctiluca, figured by Wyville Thomson as a new diatom, 

 Pyrocystis pseudo-noctiluca, x 30 (Wyv. Thorn.). 



46-53. LEPTODISCUS MEDUSOIDES, Hwg. (Hertwig) 46 and 47, Two animalcules with 

 edges variously folded, nat. size ; 48, animalcule extended, x 40 ; 49, 

 zooid in vertical section, showing the thicker central and more attenuate 

 peripheral regions ; 50, segment of a similar section more highly magnified, 

 showing oblique tubular oral fossa, superiorly attached flagellum, and at 

 a a a superficial oil-like globules; 51, endoplast or nucleus of adult animal- 

 cule, x 100; 52 and 53, supposed developmental phases of Leptodiscus, 

 with, in the former instance, one-half of the cyst-like body-wall contracted. 

 54. PYROCYSTIS FUSIFORMIS, Wyv. Thomson. Probably the encysted condition 

 of Leptodiscus, X 35 (Wyv. Thorn.). 



