90 W. G. RIDEWOOD AND H. B. FAMTHAM. 



sporulation, however, is distinctive, and of considerable im- 

 portance in determining the systematic position of the para- 

 site. 



All the pansporoblasts in a trophozoite of Neurospori- 

 dium are formed, by internal segmentation, at the same 

 time. They then commence to increase in size, growing at 

 the expense of the protoplasmic ground mass of the tropho- 

 zoite. Each pansporoblast becomes less well-marked in out- 

 line ; its protoplasm is still rather homogeneous (non-granu- 

 lar), but deeply staining, and its centrally-placed nucleus 

 divides and discharges chromidia throughout the cytoplasm 

 of the pansporoblast. Each pansporoblast thus becomes a 

 spore-morula, for the division of its nucleus into groups of 

 chromidia, or small portions of chromatin (daughter-nuclei), 

 results in the formation of many small unicellular sporoblasts, 

 distributed not only peripherally, but throughout the sub- 

 stance of the pansporoblast, as may be seen by careful 

 focussing. 



The division of the nucleus of the pansporoblast is not of 

 the serial karyokinetic type, first into two, then into four, and 

 so on, but is a kind of simultaneous '' multiple fission " of the 

 reproductive chromatin into groups of chromatin forming the 

 nuclei of the many sporoblasts, each of which soon becomes 

 a spore with little or no further differentiation. The vegeta- 

 tive chromatin of the nucleus of the pansporoblast remains 

 in the centre of the spore-morula; it is a pale-staining body, 

 and cannot be recognised until the spores have scattered 

 (see fig. 14, r.n.). 



Each spore is about 1 fx or 2 /x in diameter, and stains 

 deeply ; its small nucleus is surrounded by hyaline proto- 

 plasm. From a full-grown trophozoite a very large number 

 of spores is formed, since the trophozoite gives rise to many 

 pansporoblasts, and each pansporoblast grows and divides 

 into many spores. A full-grown trophozoite containing 

 spore-morula) in sporulatiou is more or less spherical, and 

 measures about 40 /u to 70 ^ in diameter (figs. 12 and 13). 

 The spore-morulse are spherical, and lO^u to 15ju in diameter. 



