THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 81 
of granules originate. During the subsequent progress in development 
up to the ripe psorosperm, changes take place in the form of the vesi- 
cles, the character of the contour, and the contained corpuscles. The 
latter first elongate, one pole becomes sharpened, the whole corpuscle 
assumes the familiar clearness of outline, the granules diminish in 
number and form (perhaps through fusion or after previous solution) 
the 4 capsules. The contour of the sporoblast also becomes sharp. 
Lieberkiihn (see Chloromyxum mucronatum, p. 265) first noted the pan- 
sporoblast as a solid plasma-sphere, but he did not trace the connection 
of the solid sphere with Leydig’s vesicles. 
In 1880, Gabriel noted, in Myxridium lieberkiihnii (see p. 287), that the 
vacuole stage of the pansporoblast is a subsequent and not the original 
condition. It is quite evident, however, that he did not understand 
the mode of pansporoblast formation. 
In 1881, Biitschli' showed that the pansporoblast is primarily not a 
vacuole, but a plasma-sphere. The segmentation of this and the devel- 
opment of the resulting sporoblasts were also traced. 
PROCESS.? 
Formation and segmentation of the pansporoblast.—The first step in 
pansporoblast formation is the condensation around each of the numer- 
ous nuclei (of the endoplasm) of a smail clear-contoured sphere of myxo- 
plasm, which seems limited by a thin envelope resulting from a conden- 
sation of its peripheral layer, the whole constituting a pansporoblast. 
This subsequently shrinks slightly, so as to appear as a ball surrounded 
by a vacant space, and this latter in its turn by the membrane. The 
nucleus then divides (by karyokinesis) and redivides so that one yery 
soon has a sphere (pansporoblast) with a dozen nuclei. The sphere 
then segments into two hemispheres (sporoblasts) which remain sur- 
rounded by the original pansporoblast membrane. Each sporoblast 
contains several nuclei (see below). The nuclei which do not enter into 
the formation of the two sporoblasts are rejected and are found in a 
small mass of protoplasm which remains (along with the two sporo- 
blasts) within the original pansporoblast membrane. 
In this connection it is well to quote from Kunstler and Pitres? tiie 
following erroneous description: 
This envelope [the ectoplasm] would contain, according to Biitschli, small nuclei. 
The nuclei, in proportion as the cyst [membraned myxosporidium] enlarges, divide; 
the protoplasm is condensed around them to form oval bodies, which Balbiani considers the 
spores; this author has indeed seen there the formation of four falciform corpuscles [italics 
my own, for errors]. 
‘Ztschr. f. wiss. Zool., xxxv, pp. 645-646; Bronn’s Thier-Reich, 1882, 1, p. 596. 
> Description based upon Thélohan’s (Compt. Rend. Acad. Sci. Paris, 1890, CxI, 
p. 693). For the process in the Cryptocystes, see p. 201, 
3 Journ. de Microgr., 1884, vill, p. 474, 
Fc 92 6 
