. Protozoo?logy. Protozoa; Protozoa, Pathogenic. PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 99 differences to take into account, the use of the term spore has been very ambiguous and misleading, and protozoologists have given it up for two other terms, sporozoite and merozoite, now generally adopted. The term sporozoite is used to designate those spores or germs that are Fig. 36. Life cycle of Coccidium schubergi. (After Schaudinn.) .Sporozoites penetrate epithelial cells, and grow into adult intracellular parasites (a). When mature, the nucleus divides re- peatedly (6), and each of its subdivis
. Protozoo?logy. Protozoa; Protozoa, Pathogenic. PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 99 differences to take into account, the use of the term spore has been very ambiguous and misleading, and protozoologists have given it up for two other terms, sporozoite and merozoite, now generally adopted. The term sporozoite is used to designate those spores or germs that are Fig. 36. Life cycle of Coccidium schubergi. (After Schaudinn.) .Sporozoites penetrate epithelial cells, and grow into adult intracellular parasites (a). When mature, the nucleus divides re- peatedly (6), and each of its subdivisions becomes the nucleus of a merozoite (c). These enter new epithelial cells, and the cycle is repeated many times. After five or six days of incuba- tion, the nierozoites develop into sexually differentiated gametes; some are large and well stored with yolk material {d, e, f); others ha^-e nuclei which fragment into many smaller par- ticles ("Chromidien"), each granule becoming the nucleus of a microgamete or male cell {d), h, i, j). The macrogamete is fertilized by one microgamete ((/), and the copula immediately secretes a fertilization membrane which hardens into a cyst. The cleavage nucleus divides twice, and each of the four daughter nuclei forms a sporoblast (A-) in which two sporozoites are produced U). produced after fertilization, while merozoite is used for the asexually produced germs. The protected sporozoites have the power to carry the disease from one host to another, while the merozoites, as a rule, carry the infection only from one part of the host to another part (Fig. .36). Sporozoites, therefore, have the full potential of vitality. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Calkins, Gary N. (Gary Nathan), b. 1869. New York and Philadelphia, Lea & Febiger
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