32 PRACTICAL PABASITOLOGY 



convenient for demonstration purposes and especially for section- 

 cutting, the cnidospores and especially the pansporoblasts, being 

 separated from one another by a larger quantity of endoplasm than 

 is the case with the parasite found in the gills. 



(2) Myxobolus cyprini, Dofl. Parasitic in the kidney of the carp 

 and was considered by Hofer to be the originator of small-pox, a view 

 which has since proved erroneous. 



(3) M. pfeifferi, Thel. Para- 

 sitic in the muscles of the barbel. 

 It gives rise to large tumours, 

 provoking severe pathological 

 symptoms, which frequently end 

 in death. 



(4) Lentospora cerebralis 

 (Hofer). Kesembliiig Myxo- 



FIG. 5. -Formation of cnidospores of Mus but differentiated by the 



Myxobolus pfeifferi (after Keysselitz). Mag- vacuole, which does not stain 



nified about 2,500 : 1. a, Pansporoblast with --u i- T> 4.1, 



14 nuclei, at the end of nuclear division. Wlth iodine. Parasitic in the 



b, Young cnidospore, not yet fully de- cartilaginous portions of the 



veloped, with 2 sporoplasmic nuclei 2 in? , ' - c /^ -i 



nematocystic nuclei, and 2 shell nuclei. sku11 of certain varieties of Gadus. 



A large vacuole is seen in the sporoplasm. Has been transmitted to young 



Salrnonidse in fisheries by feed- 

 ing them with infected fish -meal, when it gave rise to a disease, the 

 symptoms of which resemble gid and which is known in Germany as 

 " Drehkrankheit." Both the affected cartilage (skull, in the region 

 of the centre of hearing) and the skeleton in its immediate vicinity 

 (vertebrae of the neck, gill-cover, gill-arches) became destroyed by 

 granuloma. 



Order 3. Actinomyxidia. 



The Actinomyxides are interesting on account of the unusual 

 formation of their cnidospores. The five species known to us are 

 parasitic in certain varieties of the Oligochsetes family of the 

 Tubificidae ; four of them being found in the intestinal epithelium 

 of freshwater worms, while the fifth inhabits the body-hollow of a 

 marine worm. The cnidospores vary with the species, some being 

 round, others furnished with processes of different kinds, which may 

 give the whole cnidospore the form of an anchor. They are, how- 

 ever, always eight in number and are arranged like a three-rayed 

 star ; they are furnished with a trivalve shell ; and they have three 

 nematocysts arranged together at one pole. 



Fresh material should be carefully teased out. Cover-glass 

 specimens and sections should be finished damp, the former to be 

 prepared from teased-out portions of organs, the latter to be cut in 

 series through the entire body of the infected worm. 



