450 MRS. H, L. M. PIXELL-GOODRICH ON 



stage. This change is affected hy the breaking wp of a mass of 

 chromatin into granules, some of the smaller ones of which pass 

 to the periphery, where a distinct membrane appears. The 

 central chromatin generally forms two or three distinct masses, 

 often connected with the membrane by fine strands. These 

 vesicular nuclei are more or less oval, and their longer diameters 

 are slightly less than 3^. 



Occasionally, forms have been seen in which the nuclei are 

 massed in the centre, leaving a clear peripheral border of 

 cytoplasm. In addition there is sometimes a cavity in the middle, 

 but the nuclei are not ai'ranged in a definite single layer round 

 this cavity as described by Alexeieff (1, p. 36, fig. 4) for his 

 " plasmodes blastuloides " in Ichthyosporium gasterojyhihim. In 

 Minchinia the occurrence of the central cavity, at any rate, 

 appears to be an artifact. 



When preparing to divide a nucleus of this vesicular type in- 

 creases in size and a bundle of a,chromatic threads appeals along 

 the greatest diameter acting as a kind of spindle. The chromatin, 

 after ari'anging itself on this spindle, is drawn to the poles. The 

 vesicle then constricts in the middle, and the two ends are finally 

 nipped off as daughter nuclei. This process has been beautifully 

 figured by Granata (8, Plate 3) for Ilaflosiporidhmn limvodrili, in 

 which, according to the magnification given, the nuclei aie con- 

 siderably larger than those of Minchinia. 



After a time the c5'topla&m separates and collects round these 

 nuclei either singly or sometimes in clumps of from two to seven 

 or eight. Occasionally a dozen or so different sized masses have 

 been seen inside a cyst and have been set free by bursting it. 

 When compressed, these masses are seen to contain varying 

 numbers of nuclei. Ultimately, however, such multinuclear 

 masses are resolved into uninuclear bodies which appear at times 

 to be distinctly amoeboid. These are the gametes. No residuum 

 is left over except the chromatoid granules, which do not become 

 transformed into vesicular nuclei as already described. 



(2) Syngamy and formation of zygotes. 



The gametes proceed to pair. Fusion of their cytoplasm first 

 takes place to form a single body with still separate niiclei (PI. I. 

 fig. 5 a) for which the term Prozygote has been proposed (16). 

 Caullery and Mesnil (2) hesitated to give a definite opinion as to 

 whether similar bodies with two nuclei in some of their Haplo- 

 sporidia represented forms undergoing division or gametes under- 

 going syngamy, because they also found masses with four nuclei 

 in some cases. The same difiiculty presents itself in Minchinia ; 

 but, after prolonged study of living stages and careful measui-e- 

 ments of the different sized bodies and nuclei contained in cysts, 

 the above seems the only possible interpretation. Caullery and 

 Mesnil's forms with four nuclei (2, fig. 43) seem to be stages in 

 the formation of the sporoblasts as described below (figs. 7 & 8)., 



