THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. ila iy 
SPECIFIC CHARACTERS. 
Spore-form: This is a somewhat variable character, e. g., elliptic 
spores, varying in breadth; nevertheless, considerable dependence may 
usually be placed upon it. 
Tail: I have elsewhere (p. 207) indicated my belief that the presence 
of a tail is a good specific character. The length of the tail relative to 
that of the body (caudal index) will also prove useful. 
Ridge index: As the width of the ridge bears a very constant ratio 
to the whole width of the surface of which the ridge forms a part, this 
ratio is a good specific character, especially as it often differs markedly 
in different species. 
Capsular index: This is a character of great constancy, and hence of 
much taxonomic value. 
Nuclei: The presence or absence of the pericornual nuclei has proved 
constant in several species examined by me (see p. 210). The position 
of the remaining nuclei is inconstant. 
VI.— PATHOLOGY. 
Pfeiffer says! that myxosporidian infection is characterized by the 
rapid disappearance of the nuclei of the infected cells, the infection of 
the red blood corpuscles, and the attacking of all the elemental tissues 
of the host, with the possible exception of those of the nervous system; 
further, through the early spore formation which is unconnected with 
any external evidence of maturity. And, further, considering how the 
blood parasites of mys, Lacerta, birds, and of malarially diseased cattle 
and men,employ the blood-corpuscle membranes as protective coverings 
for their naked bodies; also, that the youngest myxosporidia, just 
out of the spore shell, attack the red blood corpuscles; and, further, 
that the JMyxrosporidia spare no organ or elemental cells (the nervous 
system possibly excepted), the destructiveness of this group of para- 
sites must be recognized to be very great; and, further, that the para- 
site withdraws directly or indirectly a large quantity of blood from the 
host, is Shown by the hematoidin crystals found in all myxosporidia, 
Finally, a cachexia, comparable with the cancerous cachexia of the 
warm-blooded animals, is produced. 
By a reference to p. 187 it will be seen that Korotneff observed in 
the polyzoan, Alcyonella fungosa, substantially the same process that 
Pfeiffer records in Lucius luctus, viz, an intracellular development dur- 
ing the earlier myxosporidium stages. 
Mode of infection —Leydig? remarked that an organism like Gen. 
incert. sp. 4. could pass with the blood current into the various organs, 
effect alodgment, become encysted, and give rise to the “ psorosperms.” 
1 Die Protozoen als Krankheitserreger, 1890, 1 ed., pp. 48-49; 2 ed., 1891, p. 135. 
2Miiller’s Archiv, 1851, p. 229. 
