118 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 
Lieberkiihn! believed that such ameeboid organisms attach themselves 
to the skin for the purpose of reproduction. Ludwig? thinks that the 
greater frequency of occurrence on the gills indicates a greater ease 
of infection through this channel than via the alimentary canal. Also 
he says: 
The lymph channels of the connective tissue appear to represent the principal 
paths through which the parasite spreads itself further through the body. 
He, however, fails to give any actual evidence in favor of this view. 
Pfeiffer * says: 
The common occurrence of the Myxosporidia in all organs presupposes a distri- 
bution via the circulation, amode demonstrated by the infection of the red blood 
corpuscles.‘ 
Effects—Upon this Balbiani’ has the following: 
Unlike the Gregarines and the Coccidia, the psorosperms spread themselves through 
almost all the organs, the deep as well as the superficial, the skin, spleen, kidney, 
air bladder, and even the heart and ovary. They are also found in the cells of the- 
urinary tubules, and in the young Graafian follicles, which they transform into a 
pocket filled with psorosperms. As at the same time they increase with great rapid- 
ity, it results that animals thus infested present grave diseases and may even die. 
Certain morbid states of fish ought without doubt to be attributed to the Myxospo- 
ridia. Such is the case of that Merluche® observed by J. Miiller and which was 
remarkable for an extraordinary emaciation. I have myself often seen roach, tench, 
and other fishes reduced by these parasites to a cachectic state characterized by a 
decoloration of the tissues, destruction of the red blood globules, and augmentation 
of the white globules; a veritable leucocythemia. It is not, then, surprising that 
this disease can cause great ravages among fishes, above all in the young, which are 
most often affected. Nevertheless this cause is not usually noted as among those 
which destroy fishes. This is easily explained; when the disease reigns attempts are 
first made to explain it by macroscopic causes and ordinarily it is the worms which 
are accused. This was the case in the epidemic of the tench in the étangs of Dombes; 
it was the Ligules which interfered with digestion and the fishes died of inanition. 
Microscopic causes are not the ones most frequently suspected. I believe that more 
frequent search would reveal microscopic lesions capable of explaining the mortali- 
ties of. young fish, particularly those living in marshes and in aquaria. 
Upon this point M. Thélohan* remarks that these parasites are gen- 
erally well borne, but that sometimes the tumors may cause death by 
pressure effects, e. g., he saw a cyst in Gasterosteus aculeatus produce 
fatal pressure upon the heart. 
The principal extensive epidemics have been those involving the 
barbels and the crayfishes (see pp. 197, 231). 
1 Miiller’s Archiv., 1854, p. 357 (see also p. 185). 
2 Jahresber. d. rhein. Fisch.-Vereins, 1888, pp. 33-4. 
3 Die Protozoen als Krankheitserreger, 1890, 1 ed., p. 48. 
4¥For the latter see p. 288. 
* Journ. de Microgr., Paris, 1883, viI, pp. 280-281. 
6] have elsewhere noted this error (p. 172). The fish in question is Gadus morrhua 
and not Merlucius merlucius. 
7Annal. de Microgr, 1890, 11, p. 203. 
