THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 121 
Plane, transverse:! Vertical and (usually) post-capsular in position, 
dividing (roughly) the spore into a capsular (anterior) and a sporo- 
plasmic (posterior) portion. 
Plane, vertical: Longitudinal and intereapsular, passing between the 
capsules and through the ends of the spore and the median cornua of 
the sporoplasm, and dividing the spore into a right and a left half. 
Posterior: See Anterior. 
Protocysts: The two smaller segments of the Myxvobolus sporoblast, 
which ultimately form the capsules. 
Protosporoplasm: The larger segment of the Myvobolus sporoblast, 
which ultimately forms the sporoplasm. 
Ribbon: The shell processes described by Balbiani in Myxobolus ellip- 
soides (see pp. 223). ' 
Ribbonettes: The terminal subdivision of the ribbons, termed 
“filaments” and confounded with the capsular filaments by some 
writers (see pp. 87, 88, 263), 
Ridge: The ridge or “ welt” which extends around the circumference, 
and marks the line of junction of each valve. 
Ridge index: The ratio of the width of the ridge to the total width 
of the surface on which the ridge is situated. 
Seat: This term invariably denotes the organ or part of the body in 
which the myxosporidian is located (see Neo Host). 
Sporoblast (and pansporoblast): This term was first used (in the 
Myzxosporidia) by Biitschh? for the transparent spherical globule formed 
by the condensation around one of the nuclei, of a portion of the sur- 
rounding myxoplasm. The spherical Siopele so formed subsequently 
segments into two hemispheres (see p. 81), each of which gives rise to a 
spore. Now, Balbiani,*? and Thélohan,* and Henneguy and Thélohan, ® 
apply the term sporoblast to the two hemispheres. Further, Pfeiffer 
uses the term sporoblast as a synonym for the whole sporing myxospori- 
dium. This latter use of the word should, I think, be unhesitatingly 
rejected as having no warrant in analogy. By the advice of Dr.C. W. 
Stiles (who has specially studied the equivalence of this and several 
other terms‘), [ have followed the lead of Balbiani and Thélohan in 
restricting the term sporobiast to the segments (the two hemispheres 
above mentioned) formed by the division of the primitive sphere. For the 
latter (the sporoblast of Biitschli) the term pansporodlast is here used. 
1 Equatorial plane of Lutz, 1889, Centralbl. f. Bakt. u. Parasitenkde, v, p. 86. 
?Bronn’s Thier-Reich, 1882, 1, p. 596. He says: ‘Since the spores originate from 
the plasma globules, we may conveniently term them sporoblasts.” Compare also an 
exceedingly obscure sentence in Biitschli’s next paragraph. 
3 Journ. de Microgr., Paris, 1883, v1, p. 275. 
4Compt. Rend. Acad. Sci. Paris, 1890, ext, p. 693. 
5 Annal. de Microgyr., Paris, 1892, Iv, p. 634. 
6 Die Protozoen als Krankheitserreger, 1890, 1 ed., pp. 32, 34, et al. 
7 Notes on Parasites; Journ. Compar. Med. & Veter. Archives, New York, 1892, x1m, 
pp. 921-324. 
