222 GARY N. CALKINS. 



the fifth place we should expect to find the daughter karyosomes 

 elongated in the axis at right angles to the .plane of division if it 

 were division. Such is not the case as inspection of the figures 

 shows, while in many cases the two karyosomes are elongated in 

 an opposite direction (Fig 2, d; Fig. 3, c). In the sixth place if it 

 were division we should expect it to take place more rapidly than 

 the figures indicate, for in fusion, the process in protozoa re- 

 quires a longer time than does division and the large number of 

 double forms of these secondary nuclei indicates that the process 

 is a relatively slow one. 



On the whole, therefore, I believe the evidence justifies no 

 other conclusion than that this is a process of fusion and not of 

 division and that we are dealing here with an actual conjugation 

 of nuclei. The fusion takes place by preliminary union of the 

 extreme peripheries, this is followed by union of the homoge- 

 neous portions, and finally by union of the karyosomes (Figs. 2, 

 3). In one or two cases I have seen some evidence that more 

 than two nuclei may thus fuse. Fig. 2, e, for example presents 

 such a case, the larger size, and the two karyosomes indicating 

 that fusion of two nuclei has already taken place. It occurred 

 to me that the minute nuclei, before fusing, might possibly divide 

 in some form of maturation division, but I have been unable to 

 confirm this supposition in the material at hand, and incline to 

 the belief that fusion occurs at once, for the uniting nuclei are 

 abundant in the immediate vicinity of disintegrating primary 

 nuclei. 



The result of this fusion of gametic nuclei is, in each case, a 

 nucleus of somewhat larger size in which the central granule 

 fragments into a cloud of extremely minute chromatin granules 

 lying about a central space which is the beginning of the vacuole 

 characteristic of the later phases in development of the spores 

 (Figs. 9, 10, 14). These granules next collect in small aggre- 

 gates which are arranged about the periphery of the vacuolated 

 mass, from 70 to 100 of them, as nearly as I can estimate, being 

 formed in each of the many centers which now correspond to 

 those multiplication centers of sporozoa called sporoblasts by 

 Schaudinn. In this period, the sporulating centers or sporoblasts, 

 are carried about in the cytoplasmic flow and appear as small 



