88 W. G. RIDEWOOD AND H. B. FANTHAM. 



our Neurosporidium consists of preserved material only, 

 Bertram ia was described from living specimens.' 



In the larger and older multinucleate trophozoites the 

 nuclei and their surrounding zones of clear cytoplasm are 

 distinctly seen (fig. 9), marking the beginning of the segrega- 

 tion of the plasmodial mass into pansporoblasts. 



The term pansporoblast was first employed by Gurley " in 

 connection with the Myxosporidia (in the wider sense, includ- 

 ing Microsporidia). A pansporoblast (' sphere primitive' of 

 Thelohan) may be described as a spore-mother-cell differenti- 

 ated within the substance of the ti'ophozoite, destined to give 

 rise to sporoblasts, from which spores are developed. (The 

 term sporoblast is applied to cells which develop each into a 

 single spore, and the term pansporoblast is applied to a cell 

 which by division gives rise to sporoblasts.) In the Myxo- 

 sporidia the differentiation takes place by the concentration 

 of cytoplasm around one of the nuclei of the endoplasm, and 

 as a rule the protoplasm becomes more transparent. The 

 pansporoblasts of a trophozoite may be many or few, or even 

 a single one. A greater or less amount of the protoplasm of 

 the trophozoite usually remains over, together with a number 

 of residuary nuclei of the endoplasm, although in some 

 Microsporidia, e. g., Thelohania and Pleistophora, the 

 whole trophozoite becomes converted into a single pansporo- 

 blast. In the typical Myxosporidia each pansporoblast gives 

 rise ultimately to two spores; in the Microsporidia, on the 

 other hand, each pansporoblast may give rise to four, eight, 

 or a larger number of spores.^ 



The term pansporoblast may be extended in its applica- 

 tion to the Haplosporidia, for although in Bertramia the 



^ See also Warren, E., "On Bertramia kirkmani," 'Annals Natal Gov. 

 Mus.,' vol. i, London, 1906, pp. 7—17. 



2 Gurley, R. R., "On the Classification of tiie Myxosporidia," 'Bull. U. S. 

 Fish. Comm. Rept. for 1891,' xi (1893), pp. 407—420: see his footnote on 

 p. 408. 



3 Except perhaps in Nosema pulvis. See Perez, Ch., "Microsporidies 

 parasites des crabes d'Aicachon," ' Soc. Sci. d'Arcaclion, Stat. Biol.,' ann. 

 viii, Paris, 1905, pp. 15— 30. 



