GENERAL ORGANIZATION 775 



described S. fnelusince from the body cavity of Simulium reftans. The 

 smallest uninucleated forms measured 5 to 7 by 3 to 4 microns. This 

 develops into a multinucleate plasmodium, which becomes enclosed in 

 a cyst from 25 to 70 microns in diameter. Within the cyst the plas- 

 modium divides into a large number of the uninucleate forms. Stempell, 

 describing the parasites from the crustacean Herpetocypris strigata, has 

 noted the formation of spores which differ as regards their shape, external 

 markings, and contents. He recognizes several genera. 



A parasite in the form of small uninucleate bodies and multinucleate 

 spheres was discovered by Calkins (1900) in the lymphatic system of trout 

 which were dying in an epidemic. Calkins gave the name Lymphospori- 

 dium truttce to the parasite. The parasite which Woodcock (1904) dis- 

 covered in plaice and flounders in the form of small white nodules on the 







./■ 



Fig. 334. — Helieosporidimn parasiticmn (x about 3,000). (After Keilin, 1921.) 



1-6. Stages in schizogony. 



7. Mature spores with coiled filament and three amoeboid bodies. 



8. Ruptured spore showing escape of filament. 



surface of the internal organs was named by him Ly mpJiocysfis joJinsfonei. 

 The nature of the organism is not known, some thinking it to belong to the 

 Microsporidiida. 



A curious parasite, Helicosporidiumparasiticum, has been described by 

 Keilin (1921) from thelarvse of Dasyhelea obscura, a ceratopogon (Fig. 334). 

 The body spaces of the larvae are invaded by small round cells, which 

 multiply by schizogony. The schizonts are 4 microns in diameter, and give 

 rise to four to eight merozoites. The remarkable feature of the parasite 

 is its spore, which is a spherical body 5 to 6 microns in diameter. The 

 capsule encloses four cells, three of which are amoeboid, while one develops 

 into a long coiled and resistant filament which appears to be free within 

 the cyst. When the host dies, the spores rupture apparently by aid of 



