THE MYXOSPORIDIA, OK PSOROSPERMS OF FISHES. 



187 



I am indebted to the kindness of Dr. Wittniack for this reference. 

 Hahiiat. — Branchiii". of Stizostedion lucioperca (pike perch). 



24. Genus et sp. incert. 



Cyst of branchial "copiiles" of Gasierosicns aciileaius Tli61ohan, 1890, Amial. 

 de Microgr., ii, p. 203. 



No description. 



Effects. — Pressure on the lieart caused death. 



Habitat. —Branchial " copules" of Gastcrosteus acuJeatus (stickleback). 



25. Genus et sp. incert. 



Psorosperms of mackerel, v. d. Borne, 18SG, Handb. d. Fisclizuchtu. Fisclierei, 

 p. 211. 



No description (cf. p. 172). 



Hahitat. — On Scomher scomhrus (mackerel). 



26. Gen. incert. ("Myxosporidium") bryozoides Korotneff, 1892. Pis. 8, 9. 



Myxosporidium f {development of). — For study of development, the 

 polyzoan spermatoblasts offer a very rich material, comprising all 

 stages of alterations. The earliest stage (pi. 9, fig, la) is a healthy, well- 

 preserved cell, containing a large, round micleus 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 Wehenkern. The myxoplasm 

 has, Korotneff inclines to believe, from the moment of its entrance so 

 completely mixed with the i^olyzoan cytoplasm that we can no longer 

 speak of a plasma differentiation. 



The nucleus divides by mitosis (pi. 9, fig. lb). 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 nonvital and 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. 20C). 



