DEVELOPMENT OF A MYXOSPORIDIAN 341 



enclose the others, while the sporoplasm cells fuse into a common 

 mass of protoplasm; the nuclei, however, remain distinct even 

 in the mature spore (figs. 41 to 43). The capsulogenous cells 

 can easily be distinguished by the fact that the cytoplasm be- 

 comes condensed at one side of the nucleus and contains numerous 

 minute granules which stain deeply with the plasma stain (fig. 

 41). A little later a small, rounded, deeply staining body ap- 

 pears in the concentrated cytoplasmic mass (fig. 42). At a 

 somewhat later stage this body becomes differentiated into a 

 clear space surrounding a central, deeply staining part which is 

 evidently the developing thread of the capsule (fig. 43). 



Sporoblast cells undergoing mitotic division are common in 

 sectioned material so that the details of the process can be easily 

 worked out. During the prophase (figs. 48 and 49) the chro- 

 matin forms a coiled spireme. Apparently there is more than 

 one of these chromatin threads, although there are certainly not 

 as many as there are distinct chromosomes later. Usually the 

 spireme can be traced into one or more irregular masses of chroma- 

 tin imbedded in achromatic material. These masses are prob- 

 ably disintegrating nucleoli, the chromatin of which is taking 

 part in the formation of the chromosomes. As indicated on 

 page 338 — the nuclei are composed of two distinct materials — 

 an outer portion which shows a great affinity for chromatin 

 stains and is, in all probability, chromatin; and an inner portion 

 which stains less readily and is evidently composed of plastin. 



During the metaphase the chromosomes become arranged 

 around the equator of the spindle in the usual manner (figs. 50 

 to 52). The chromosomes are usually so closely crowded to- 

 gether as to make it difficult to count them with certainty but 

 polar views of a few exceptionally favorable cells show that there 

 are, without doubt, six chromosomes. As regards size these 

 chromosomes can be readily grouped into three pairs, one of 

 which is considerably larger than the other two, one smaller, 

 while the third pair is intermediate in size. The spindle is poorly 

 developed and at no time have I been able to find any trace of 

 centrosomes. Figure 53 shows an early, figure 54 a later ana- 

 phase. In the latter the well-defined remains of the nucleolus 



