ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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The distinctive characters of these are : — 
(1) The stage of growth is always intracellular. 
(2) A free adult form is only found in Gregarines and Haemosporidia, 
and in them thero may be conjugation. 
(3) The adult form, which is elongated and mobile in those just men- 
tioned, rounded and immobile in Coccidia, and amoeboid in Gymnospo- 
ridia, becomes encysted in all but the last. 
(4) Encystation or rounding precedes sporulation ; the contents of 
the cyst divide and give rise to 1 to n spores ; in the interior of each 
spore 1 to n sporozoites are formed. 
(5) Gregarines alone have non-intracellular cysts ; they are always 
polysporous. 
(6) The Haemosporidia always have intraglobular or intracellular 
cysts, and are always monospores. 
(7) The Coccidia and Gymnosporidia have similar cysts to 6, but 
may be indifferently mono- or polysporous, and they may, in cases of 
acute infection, undergo a precocious division. 
With regard to the parasitic process the cell is necessary for the 
development of every intraglobular parasite ; infection is effected by re- 
productive germs or sporozoites ; these may penetrate into the organism by 
the intestine or by the respiratory passages, being carried by air or water. 
Infection can always be experimentally produced from individual to in- 
dividual by injection of parasitic blood into the vessels, but not from 
one species to another. Infection is submitted to certain conditions of 
immunity, w'hich seem to have some relation to the intensity of infection ; 
phagocytosis, as a means of defence for the organism, is not generally 
exercised, but in certain cases the leucocytes do acquire a phagocytic 
power. With the exception of Proteosoma and Hsemamoeba, the parasite 
rarely has any pathogenic action on the organism ; the parasitic action 
is ordinarily limited to the infected corpuscle ; whatever be the changes, 
such as anemia, the cell easily loses its power of dividing or its special 
function in the organism. The influence of the blood-medium on the 
parasite is seen in the simplification of its structure, and by the increase 
in the number of reproductive germs. 
The following generalizations probably apply to all cases of para- 
sitism : — 
Parasitic degradation is more marked in proportion as the parasite 
has less relation with the external medium, and it is marked by these 
essential characters — simplification in structure and complexity in de- 
velopment, with augmentation of the number of reproductive germs. 
Poly tome®.* — M. Raoul France gives a monographic account of this 
family, which includes forms approximately parallel morphologically to 
Chlamydomonads and Yolvocineae, but without chlorophyll and sapro- 
phytic. The structure, functions, reproduction, bionomic relations, and 
classification are all discussed. He ranks the family in the order 
Yolvocinaceae, sub-order Chlamydomonadinae, and gives the diagnosis as 
follows : — Individuals colourless, with a sheath or a thick shell, with 
1-4 flagella. Reproduction by 1-3 vegetative divisions, and facultative 
conjugation. Genera : Polytoma , with five species, and Chlamydoblejpharis 
g. n. 
* JB. wiss. Bot., xxvi. (1894) pp. 205-378 (4 pis., 9 figs.). 
