CLASSIFICATION AND GENERAL CHARACTERISTICS 475 



so far as they increase the absorptive surface of the body, as food is 

 absorbed by diffusion. Food vacuoles or contractile vacuoles have not 

 been found. 



The life cycle of a typical sporozoan is represented after Schaudinn 

 in Fig. 143. 



A somewhat similar cycle may be followed in the study of the coc- 

 cidiuin cuniculi of the rabbit, a description of which is given below. The 

 other varieties in this group, which are parasitic in man, or which are 

 of some medical interest, and which are described below, are the 

 following: 



Various not fully studied coccidia. 



Plasmodium malariae and its allies. 



Piroplasma bigemmium and its allies. 



Nosema bombycis and nosema lophii. 



The Ciliata (See Fig. 159) belong to the most complex of the protozoa. 

 They possess a definite entoplasm containing nuclei and food vacuoles, 

 and a definite ectoplasm containing basal granules from which arise the 

 cilia which give the group its name. They have organoid structures 

 which receive the food, and some have definite mouth openings indeed, 

 and definite places for excreting waste products. The food vacuoles may 

 contain acid or alkaline digestive products. The nuclear material is 

 differentiated into two forms, a large macronucleus and a much smaller 

 micronucleus. The function of the macronucleus is supposed to be 

 vegetative, and that of the micronucleus reproductive. The macro- 

 nucleus varies in size and shape and is completely filled with an alveolar 



DESCRIPTION OF FIG. 143. 



The life cycle of coccidium Schubergl. / to VII represent the asexual reproduction or schizogony, 

 commencing with infection of an epithelial cell by a merozoite or a sporozoite; the merozoite after 

 stage VII may start again at stage //, as indicated by the arrows, or it may go on to the formation 

 of gametocytes (IX to XII). IX to XIV represent the sexual generation, the line of development 

 becoming split into two lines male 5 and female 9, culminating in the highly differentiated gametes, 

 which conjugate and become again a single line, shown in X/Vand XV. The zygote thus formed goes 

 on to the production of spores, XVI to XX. I to IV represent epithelial cells showing penetration 

 of a merozoite or a sporozoite and its change into a schizout. V, the nucleus of the schizout divid- 

 ing. VI, numerous daughter-nuclei in the schizout. VII, segmentation of the schizout into numerous 

 merozoites, about a central mass of residual protoplasm, which in this figure is hidden by the mero- 

 zoites. VIII, merozoite passing to reinfect host cell and repeat the process of schizogony. IX, X, mero- 

 zoites to be differentiated into male and female gametocytes. XIa and Xlla, the two gametocytes 

 within a host cell; the microgametocyte (5) has fine granulations; the macrogametocyte (9) 

 has coarse granulations. Xlb, an immature female gametocyte within a host cell. XIc, a female 

 gametocyte undergoing maturation, still in the host cell. XIII, mature macrogametocyte, freed 

 from the host cell, and sending a cone of reception toward an approaching microgametocyte. 

 Xllb, a full-grown micro-gametocyte within a host cell. In XIIc the nucleus of the microgametocyte 

 has divided up to form a great number of daughter-nuclei. In Xlld the nuclei of the last stage have 

 become microgametes, each with two flagella. Xlle, represents the free microgametes, swimming to 

 find a macrogamete. XIV, the zygote (fertilized macrogamete), surrounded by a tough membrane or 

 oticyst, which allows no more microgametes to enter, and containing the female chromatin, which is 

 taking the form of a spindle, and the male chromatin in a compact lump. XV, the chromatin from 

 these two sources united and no longer distinguishable as male and female. XVI, the nucleus of the 

 zygote dividing. In XVII tour daughter-nuclei are formed the nuclei of the sporoblasts. In XVIII 

 the four gporoblasts become distinct, leaving a small quantity of residual protoplasm ; each sporo- 

 blast has formed a membrane, the sporocyst. In XIX within each sporocyst two sporozoites have 

 been found about a sporal residuum. In XX, the sporozoites becoming free by bursting the sporo- 

 cysts, pass out through an aperture, in the wall of the oiicyst, and are ready to enter the epithelial 

 cells of the host. (From Lang.) 



