118 RErORT OF TITK COMMTSSloXKU OP FlSH ANl") FlSHKrilFS. 



Jiit'berkiihii' believed that sucli anueboid or^^iaiiisms attach themselves 

 to the skin lor the purpose of reproduction. Ludwij;; -' thiidcs tliat the 

 greater frequency of occurrence on the gills indicates a greater ease 

 of infection througli this channel than via the alimentary canal. Also 

 he says: 



The lymph channels of the conuective tissue appear to rejiresent the principal 

 paths through which the parasite spreads itself fiirtlicr through the hody. 



He, however, fails to give any actual evidence in favor of this view. 



Pfeiffer ^ says : 



The common occurrence of the Myxosporidia in all organs })resupposes a distri- 

 hntion via the circulatiou, a mode 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 tlirongh 

 almost all the organs, the deep as well as the superficial, the skin, spleen, kidney, 

 air bladder, and even the heai't 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 Mifxospo- 

 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 leucocythieniia. It is not, then, surprising that 

 this disease can cause great ravages among fishes, above all in the young, which are 

 most often afi'ected. Nevertheless this cause is not usually noted as ainong those 

 which destroy fishes. This is easily explained ; when the disease reigus 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 dtangs of Doujbes ; 

 it was the Ligules which interfered with digestion and the fishes died of inanition. 

 Micro8CO])ic 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, jiarticularly those living in marshes and in aquaria. 



Upon this point M. Th^lohan ^ 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 (UisterosieuH acnJeatiis produce 

 fatal pressure upon the heart. 



The principal extensive epidemics have been those involving the 

 barbels and the crayfishes (see pp. 107, 231). 



1 MiJllcr's Archiv., 1854, p. 3.57 (see also p. 185). 

 ^Jahresbcr. d. rhein. Fisch.-Vereins, 1SS8. pp. 33-4. 

 'Die Protozoen als Krankheitserreger, 1890, 1 ed., p. 48. 

 * For the latter see p. 288. 



e.Iourn. de Microgr., Paris, 1883, vii, pp. 280-281. 



*I have elsewhere noted this error (p. 172), The fish in question ia Gadiin monhua 

 anil not Merlvcius merluciits. » 



» Annal. de Microgr, 1890, ii, p. 203. 



