'Then the ichthyophthirius has reached raaturitv in the skin, v/hich at lO'C. according 

 to my observations may require three v;eeks and longer, it separates from the fish, falls 

 to the bottom, fastens itself in the pond and divides itself into about 1000 progeny of 

 30 gu size, vrtiich as "swamers" berin to swini about freely 21^ hours after their release 

 and seek r\sr, fishes. They can easily be carried avray by flovdng v;ater. Sixty hours 

 after release and encystiaent, I have not been able to observe any living svrarrners« 

 Obviously the;,^ die very soon, as surmised by Buschkiel 1910, Little fishes in densely 

 stocked brood ponds are naturally very much endangered with the occurrence of ichthy- 

 ophthirius . 



Pbrthemore, it often happens that brood ponds and brood channels which are fed out 

 of non-drainable village or mill ponds, in wliich there are fishes v/ith a latent infection 

 of ichthyophtidrius beccxne so infested every j'ear that the rearing must be given up. 

 Ichthyophthirius easily becomes so firmly established even in experimental basins and 

 ponis that it v/ill not disappear for years. It then easily causes epidemics of sickness « 



An epidemic must be avoided from the very beginning by the health maintenance of the 

 spawn fishes, and the avoidance of parasite containing inflor; water. Holding of the 

 diseased brood in boxes which have a strong thi-ough flow at the bottom, causes the 

 parasites to wash away as fast as they fall off and thereby leads to recovery of the 

 brood often v.'ithin two to three v.'eeks, Sy bathing the brood in a solution of 1 gran of 

 quinine sulphate in 10 liters of v;ater all the parasites v;hich drop off are safely 

 killed v/ithin one to tv/o hours vfithout injuring the fishes. 3iit this bath can hardly be 

 used practically, because it must last two to three weeks. In that case aeration would 

 have to be provided for. The solution remains active, 



Corta'~ious Inflar.iriation of the Cornea . In many localities, particularly in the 

 H.irz, a v:hitii-h clouding of the cornea occurs with trout, which slowly and progressively 

 injures the vision of the attacked fishes. It is to be presumed according to Fischer,, 

 that protozoans are concerned as the instigators. 



Tr:/panoplasiTia Infection . Infection of the blood with various species of trypano- 

 plasrna, a half-noon shaped, 15 imi length, parasite similar to the instigator of the sleep- 

 ing sictoess in laan, occurs in carps but especially in tenches. On closer investigation, 

 I fornd in 1 cubic millimeter of blood from a half pound tench up to 0.11 million 

 trj-panoplasna and only 0.96 million red blood cells, whereas normally there are about 

 1.7 million red blood cells present rdth tenches. The hemoglobin content was at the same 

 tL'.ie lowered frcm the normal value of 65 percent down to 55 percent. The fishes are very 

 v;eak from such an attack, and often assume a lateral position v/ith a bent dovm head, 

 become anaemic and emaciated. The eyes in particular are as a rule deeply sunken, the 

 slcin is pale. Zince the parasites are transferred by the fish leech, the destruction 

 of all the tr;-panoplasma harboring fish leeches and v;eak fishes is.necessarj' for combatt- 

 ing the disease, 



Module (ii-eases . On the skin of tenches and carps there are often many pinhsad- 

 si'-ied elevations between the two rows of gill lamellae of the individual gill arches of 

 carps, T'hese are white and the size of farina (see I-lg. 69) in carps. <>". the ends of 

 the gill lanellae of tenches, bead-like cysts, "nodules" with sporozoa (various species 

 of LI;':<obolus, and Llyxobolus pirifonr.is ) may be observed. Occasionally cysts of sporozoa 

 also occur la inner organs. The spores are mostly up to about 2 C mi in size and disk 

 shaped. They are reco;;ni::ed -jnder the microscope by their strong refractivity and the 

 possession of one to tv/o egg-shaped polar cells. With a strong attack great losses can 

 occur, especially when the respiration is retarded by the attack. V'ith a weak attack, 

 injuries of the fishes cannot he detected. Since several thousand or iTiillions of spores 

 develop in each. cy:;t reactively formed by the fish, and each of these spores can again 

 attack a fish and later cause the formation of a cyst, it is absolutely necessary to 

 prar.ptly remove all parasite carriers out of the pond fisheries before the total stocks 

 and fishes are infected. 



The sporozoa Eimeria, an intestinal parasite, often leads to severe intestinal 

 diseases in carps during the hibernation periofi. It leaves the "yellovY bodies" in the 

 intestine. 



205 



