730 THE AMERICAN NATURALIST [Vol. LI 



generating stages analogous to those found in the mono- 

 sporous, disporous and the non-disporoblastic poly- 

 sporous forms, among the debris of the dying animals 

 inside the gall and urinary bladder, as I have shown in 

 Chloromyxum leydigi. In the so-called "tumor-forming" 

 disporoblastic polysporous forms, no facts are known 

 which show that somatic residual nuclei have been ob- 

 served. The beginnings of cyst formation, however, 

 have never been studied, and it is only at this stage that 

 somatic residual nuclei may be seen, and not after the 

 cyst is crowded with sporoblasts and spores. But even 

 in the fully developed cysts there may be degenerating 

 somatic residual nuclei which have escaped observation. 

 The facts which Weissenberg found in Glugea anomala 

 and hertwigi—two Microsporidia— seem to support my 

 suggestion. But the HuUzellen or Hullzellenkerne of the 

 myxosporidia are never identical with somatic nuclei. 

 Their undisputed place in the development of the myxo- 

 sporidia will soon be clear. 



Before we proceed further in discussing the formation 

 of the sporoblast membrane in those myxosporidian 

 species in which the spores are formed in pairs inside one 

 sporoblast, it may be recalled that several facts have been 

 ascertained concerning the fully discussed spore-mem- 

 brane formation in monosporous or disporous myxospo- 

 ridian species: (1) The copulation of two gametes occurs 

 during or after the two myxosporidia leave the spore. 

 (2) No reduction takes place from the beginning of spore 

 formation until the end, because the number of chromo- 

 somes remains the same (Davis and Georgevitch). (3) 

 The darkly staining masses of "restkerne," ''residual 

 nuclei," "reduction nuclei" have been shown to be gly- 

 cogenous and to be necessary for spore-membrane for- 

 mation. (4) Membrane-forming cells or nuclei are set 

 apart by different division intervals from the other cells 

 of the sporoblast. 



Now from the above given summary of the latest facts 

 in monosporous or disporous forms, it is clear that they 



