248 THE SPOROZOA 



pigment-granules. In the male crescents or microgametocytes 

 the grains of pigment are scattered evenly in the cell -body ; 

 in the female crescents or macrogametocytes the pigment is 

 aggregated at the centre, surrounding the nucleus. The crescents 

 appear to originate in the spleen and bone -marrow, but when 

 full-grown they are found in the peripheral circulation. As they 

 approach maturity the crescent -shaped gametocytes undergo a 

 change of form, becoming first oval, then spherical, and free 

 themselves in the final stage from the remains of the blood- 

 corpuscle (Fig. 68, VIII a and b, IX a and b). The changes from 

 crescent to sphere may take place in the human blood, or not 

 until transference to the intermediate host, the mosquito, has 

 been effected. In no case, however, do the gametocytes get 

 beyond the spherical stage in the human body. 



The two species of Plasmodium are at once distinguishable from 

 Laverania by the fact that the gametocytes do not take on the form of 

 crescents, but have the same rounded shape as the ordinary schizonts. 

 The various forms of the tertian parasite have recently been studied in 

 great detail by Argutinsky [61] and Schaudinn [94a], whose results are, 

 in the main, in harmony. (1) The schizonts are about 10 fj. in diameter, 

 with a nucleus usually situated excentrically, and containing at first a 

 single mass of chromatin, later a number of chromatin granules held in 

 an even achromatic network, the whole being surrounded by a delicate 

 alveolar border (sic Schaudinn ; Argutinsky characterises the nucleus of 

 the schizont as vesicular). (2) The macrogametocytes are much larger 

 (12-16 /u, in diameter), when full-grown, than the schizonts, and much 

 less amoeboid during earlier stages of growth. Their protoplasm is 

 dense and stains deeply, and their grains of pigment are two or three 

 times as large, and fully twice as numerous, as those of the schizont. 

 The nucleus, situated at the periphery, is oval or elongated in form, with 

 grains of chromatin in the nodes of an alveolar framework. (3) The 

 microgametocytes are distinguished in all stages by their very large 

 chromatic nucleus, containing coarse grains of chromatin, and situated 

 centrally. The protoplasmic portion of the body is feebly developed as 

 compared with the two foregoing, and it is less dense and stains a much 

 lighter tint. It is scarcely at all amoeboid at any stage. The melanin- 

 pigment is abundant and the grains appear larger than in the macro- 

 gamete, but according to Schaudinn this is an optical illusion. Schaudinn 

 considers the differences between (2) and (3) to be adapted to their role 

 in development. The macrogamete, like an ovum, has to provide for 

 posterity, hence its large bulky protoplasmic body. In the microgameto- 

 cyte, only the nuclear substance passes on into the next generation, hence 

 the protoplasmic body is to a large extent atrophied, while the nucleus 

 is greatly developed. 



The stages in the origin and growth of the gametocytes are still some- 

 what obscure. Mannaberg derived the crescent-form from a syzygy, i.e. 

 the union and fusion of two amoebulae, and more recently Ewing [66] 

 has maintained that unions of this kind take place between amoebulae. 



