THE SPOROZOA 225 



the macrogamete. In Klossia helicina precocious association of the 

 gametocytes occurs, but in this case the female parasite is not 

 set free from the host- cell. Several microgametocytes penetrate 

 into a kidney-cell containing a macrogametocyte, and there form 

 each four microgametes, one of which fertilises the macrogamete 

 when mature. In all these cases the economy effected in the 

 number of microgametes produced is probably related to the early 

 pairing of the gametocytes, and the consequent certainty that the 

 union of the gametes will be effected. 



In the formation and maturation of the gametes, the most essential 

 feature in the instance selected is the elimination in both sexes of the 

 karyosome, which, like the macronucleus of Infusoria, would appear to 

 represent effete nuclear substance which is cast out and formed anew at 

 conjugation. The karyosome is not, however, always eliminated before 

 the actual union of the gametes. To go no further than the Lithobius, 

 in Coccidium lacazei and Adelea ovata the karyosomes are retained in both 

 the gametes, and the same is the case in Coccidium proprium, A. Schn., of 

 Triton. In all these instances, however, the karyosomes are left behind 

 in the residual protoplasm of the oocyst, and do not pass on into spores 

 or sporozoites, so that the result is the same. In Coccidium lacazei, 

 correlated with this difference, Schaudinn observed microgametes swarm- 

 ing round immature, half-grown macrogametes, which they never do in 

 C. schubergi. 



In Cyclospora caryolytica the karyosome of the male gametocyte 

 becomes divided each time that the nucleus divides, and the nucleus 

 of each microgamete contains, at first, a distinct karyosome ; but as the 

 nucleus assumes its definitive, elongated form, the karyosome is suddenly 

 ejected from it, and is left behind by the microgamete when it swims off. 

 In the macrogametocyte of this species a very interesting process of 

 maturation takes place. The karyosome first becomes fragmented to 

 form a clump of fine granules, constituting a chromatic nucleus, which 

 divides by a primitive form of karyokinesis into two. One of the two 

 daughter nuclei divides again in a similar manner. Three nuclei are 

 thus formed, two of which become slowly absorbed in the cytoplasm, and 

 represent as it were polar bodies cast off in order to bring about a 

 process of nuclear reduction. The third remaining nucleus becomes the 

 pronucleus of the macrogamete (see also below, p. 273). 



In Adelea ovata, according to Siedlecki, the two consecutive nuclear 

 divisions to form the four inicrogametes are different from one another : 

 the first is regular and resembles karyokinesis, the second simply divides 

 the chromatin into two halves. The author believes that the first 

 division reduces the quantity of chromatin, the second the number of 

 chromosomes. In this form also a quantity of chromatin is eliminated 

 from the macrogametocyte at maturation, prior to fertilisation. Thft 

 maturation of Adelea ovata would thus seem to approach more nearly the 

 Metazoan type than does that of Coccidium schuberyi. 



In Caryotropha the microgametocyte does not divide up at once into 

 microgametes, but first into a number of spherical cells, which may be 



15 



