4 PEACTICAL PARASITOLOGY 



(ii.) By Multiple Division. The breaking up of the organism into 

 a large number of daughter-cells. Under this heading are included : 



(a) Schizogony. Multiple vegetative reproduction in the unen- 

 cysted condition, the new individuals being known as merozoites. 

 The process may be repeated several times. 



(b) Sporogony. A multiple vegetative reproduction which occurs 

 once and without immediate repetition as the result of previous 

 fecundation, and generally takes place within a cyst. The daughter- 

 individuals are known as sporozoites. 



(c) Gamogony. Multiple reproduction of sexually immature indi- 

 viduals, the progeny, known as gametes, being sexually mature. 



The combination in one species of several methods of propagation 

 constitutes an alternation of generation. 



Fecundation among the Protozoa consists in the merging of two 

 nuclei and the production of a new homogeneous unit, known as the 

 " new cell." It may take place in one of three ways : 



(i.) Copulation. The merging of two distinct individuals (gametes) 

 to form a new homogeneous individual. The sexually immature 

 individuals are known as gametocytes. Their development into 

 sexually mature, similar or dissimilar, gametes is the result of : 



(a) The reduction of the nucleus without division of the cell, as in 

 the macrogametes of the malaria parasites and the Coccidia. 



(b) Simultaneous multiple reproduction by gamogony, as seen in 

 the Gregarines and in the formation of the microgametes of malaria 

 parasites and Coccidia. 



(ii.) Conjugation. Here there is no merging of separate organisms, 

 the meeting of the two conjugating individuals being quite transitory. 

 They remain in contact only long enough to exchange portions of the 

 nucleus, a free or male nucleus passing from each into the other, 

 where it combines with a stationary, or female, nucleus to form the 

 new cell. This method is characteristic of the Infusoria. 



(iii.) Autogamy. In this case the entire process of propagation is 

 carried out by a single individual. The method varies in different 

 species, but in all cases two gamete nuclei are produced which unite 

 to form a single new cell (Amosbse, Myxosporides) . 



II. -GENERAL EEMARKS UPON THE TECHNIQUE OF EXAMINING 



PROTOZOA. 



The importance of using living Protozoa for purposes of investiga- 

 tion cannot be over-estimated. Without a knowledge of the motor 

 phenomena, it is impossible to understand in its entirety the organiza- 

 tion of certain species, such as the Amoebae, Flagellates, and Infusoria. 

 But, apart from this, there are certain peculiarities of structure which 



