THE GENEKAL SIGNIFICANCE OE AMPHIMIXIS 215 



shape (3), and then, after having devoured the cell, it gives rise, by 

 a peculiar process of division (Schizogony), to a number of very 

 minute nucleated pieces, again sickle-shaped, the Schizonts, each 

 of which bores its way into an epithelial cell as in a, and follows 

 the same path of development, so that a large number of cells in the 

 intestine of the same host ai-e attacked in this manner. But there 

 is still another mode of reproduction, with which amphimixis is 

 associated, which leads directly to the formation of ' lasting ' germs 

 which are enclosed in a capsule or cyst, reach the exterior with the 

 excrement of the host, and thus spread the infection to other centipedes. 

 The Schizonts which take this course develop into so-called macro- 

 gametes and microgaraetes, the former being the female, the latter th 

 male germ-cells. Then follows the penetration of a male gamete, 

 actively motile because of its two flagella, into the female gamete (8). 

 Amphimixis is accomplished, and the product of the fusion of the 

 two sex-cells (9) surrounds itself with a thinner cyst, within which it 

 multiplies by twofold division into four cells (10). These are the 

 ' lasting ' spores, which may dry up within the voided excrement 

 of the centipede (11), and if they be eaten by another animal of the 

 species, they infect it, for the sporozoites which have been formed by 

 the previous divisions, creep out, and in form i begin the life-history 

 anew. 



We have thus an alternation of four generations which are all 

 unicellular, and of which one series (1-5) shows multiplication by 

 fission, while the other (6-1 1) includes, besides multiplication by 

 fission and as a condition of this, the process of amphimixis. Amphi- 

 mixis ')nust occur in order that the formation of ' lasting ' spores and 

 new sporozoites may result. We have thus a regular alternation of 

 ' asexual ' and ' sexual ' reproduction, and the latter shows great 

 resemblance to that of multicellular organisms. The macrogamete 

 corresponds to the ovum, the mierogametes to the spermatozoa, and 

 they resemble these also in their greater numbers and in their 

 structure. 



But the resemblance goes even further. The ovum is much larger 

 than the sperm-cell, and undergoes a kind of reduction of its nuclear 

 substance; shortly before fertilization the ovum-nucleus ('the 

 germinal vesicle ') comes to the surface — -just as in the case of animal 

 ova— bursts, and extrudes a part of its substance in the form of 

 a sphere (Fig. 121, 6 and 7). A reduction of the nuclear substance in 

 the male cell has not been demonstrated in all cases, but in one of the 

 Lithobius-Coccidia., Adelea ovata, the relatively large microgamete 

 (the sperm-cell, Fig. 122, Mi) places itself close to one pole of the 



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