THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 95 
the great similarity between the spores and the pseudonavicelle. He 
says: 
For the further fate of our psorosperms it is not without interest to observe that 
they frequently occur free in the bile passages, while on the contrary they are no 
longer to be found in the intestinal canal, in which they, however, incontestably 
arrive. May they not here develop directly into those round worms which we not 
rarely encounter in the intestinal canal of these fishes. 
Charles Robin was the first to assert their vegetable nature. In his 
Histoire Naturelle des Végétaux Parasites (Paris, 1853, pp. 291-2, 321), 
he collected descriptions and figures of nearly all the previously 
described species, placing them (as a special tribe, the Psorospermee) 
under the Diatoms.. He says: 
Several facts have convinced me of the vegetable nature of these bodies. These 
are the entirely peculiar aspect of the species! that I have had under observation; 
the definite rupture of the coriaceous cells of which they are composed; the pres- 
ence upon some of special opercles; their contents partly homogeneous, partly 
formed of drops of oil in suspension in a clear liquid; the solubility of the walls, 
which often occurs in concentrited sulphuric acid in the manner of cellulose (although 
they are not colored by iodine). Like Miiller and Retzius * * * I believe that 
these vegetables approximate by their form and general structure to the Diatoms, 
among other forms to Navicula and Melosira, etc., although they differ in the absence 
of silica in the walls. * * * Like the Diatoms they can live either free or 
reunited into colonies. * * * Although it is probable that the species described 
below will one day form at least two genera, * * * Ishall unite them provision- 
ally [under one genus. | 
Lieberkiihn’ in his first paper expressed the opinion that the ‘ pso- 
rosperms” could not be, as Leydig supposed, Gregarines, inasmuch as 
they possessed no nucleus. In his second paper*® he again rejects 
Leydig’s view in so far as the innominate form (Gen. incert. sp. 12) found 
by him under the skin of Gasterosteus aculeatus is concerned, saying 
that: 
This mode of origin [the process of spore formation] is so peculiar that we cer- 
tainly can not reckon such formations among the Gregarines. (Their size, absence 
of structure, occurrence in water, the importance for reproduction of the granules, 
and the observed young stages, all give rise to opinions but not to certain knowl- 
edge. 
Further, it is doubtful, he says, whether any Gregarine lives in 
water, whereas in all probability the psorosperm animal does, and 
attaches itself to the skin merely for reproduction. That the ‘“ psoro- 
sperms” are not amcebe is indicated by his failure, on careful inves- 
tigation, to find any of them capable of taking up foreign bodies into 
their substance. Also, he was never able to find an amceba which had 
just attached itself to the skin preliminary to reproduction. He con- 
cludes by saying that his researches on the parasites of fresh-water 
sponges promise to throw light on this subject, as he has there found 
large psorospermiform bodies consisting of small and large globular 
1 Psorospermia sciene-umbre Robin (see p. 166). 
2 Miiller’s Archiy., 1854, p.5. 
8 Ibid., pp. 357-367. 
