THE MYXOSPORIDIA, Ok PSOROSPERMS OF FISHES. 187 
I am indebted to the kindness of Dr. Wittmack for this reference. 
Habitat.—Branchiz of Stizostedion lucioperca (pike perch). 
24. Genus et sp. incert. 
Cyst of branchial ‘“‘copules” of Gasterosteus aculeatus Thélohan, 1890, Annal. 
de Microgr., 0, p. 203. 
No description. 
Effects.—Pressure on the heart caused death. 
Habitat.—Branchial “ copules” of Gasterosteus aculeatus (stickleback). 
25. Genus et sp. incert. 
Psorosperms of mackerel, v. d. Borne, 1886, Handb. d. Fischzucht u. Fischerei, 
p. 211. 
No description (ef. p. 172). 
Habitat.—On Scomber scombrus (mackerel). 
26. Gen. incert. (“‘Myxosporidium’”’) bryozoides Korotneff, 1892. Pls. 8, 9. 
Korotneft's | . 
a ae | bryozoides.| Date. Authority; reference. 
Jungosa. 
Myxospo- 
ridium*.| 1892 | Ztschr. f. wiss. Zool., LIIT, pp. 591-6, pl. 24. figs. 1-12. 
Do ....| 1892 | Henneguy & Thélohan, Annal. de Microgr., IV, p. 617. 
Dor. Sa: |v 1893 Braun, Centralbl. f. Bakt. u. Parasitenkde, XIII, p. 97. 
x 1893 | Ohlmacher, Journ. Amer. Med. Assoc., XX, p.562. 
x 1893 | Braun, Centralbl. f. Bakt. u. Parasitenkde, XIV, p. 739. 
Myxosporidium ? (development of).—For study of development, the 
polyzoan spermatoblasts offer a very rich material, comprising all 
stages of alterations. The earliest stage (pl. 9, fig. 1a) is a healthy, well- 
preserved cell, containing a large, round nucleus and, lying near it, the 
nucleus of the intruded myxosporidium, which latter is small, elongate- 
oval, dark-staining, and which, but for the complete series of changes 
exhibited by it, might be supposed to be a Nebenkern. The myxoplasm 
has, Korotneff inclines to believe, from the moment of its entrance so 
completely mixed with the polyzoan cytoplasm that we can no longer 
speak of a plasma differentiation. 
The nucleus divides by mitosis (pl. 9, fig.1b). Simultaneously or some- 
what later the polyzoan cell-nucleus divides, but this latter division is 
never by mitosis, and is rather to be regarded as an externally induced 
fragmentation. The nonvitaland artificial character of the cell-nucleus 
- division is further shown by the variable size of the nuclei, resulting 
from the division, the nucleus having lost the capability of growth. 
Its division results from an irritation of, or better, an impulse from, the 
presence of the intruded myxosporidium. This artificial stimulation of 
the powers of the infected cell constitutes the peculiarity in the action 
of the parasite which thus prepares for itself an artificial ground with- 
out which its existence would be impossible. Sometimes cell-nucleus 
division takes place somewhat later than that of the parasite, so that 
we already find the parasite with 4 daughter nuclei (1 of which was’ 
* Name not in good standing (see p. 206). 
