ACTINOMYXIDIA 



529 



pansporoblast. The nucleus of the pansporoblast divides repeatedly, after 

 which the cytoplasm splits into two masses — the sporoblasts — each of which 

 is covered by a cuticle and contains three nuclei. 



The cytoplasm of the sporoblast now divides into three areas around the 

 nuclei. One of these areas is large, and is called the sporoplasm, while the 

 other two a,re small, and form the polar capsules. Each spore, therefore, 

 contains two polar capsules and one mass of sporoplasm, which represents a 

 single sporozoite. Each polar capsule develops a spirally coiled thread. A 

 spore escapes when the parent trophozoite dies, and then finds its way out of 

 its host by the bile or urine, or through the tissues into the alimentary canal. 

 For further development it must be swallowed by another host, in whose ali- 

 mentary canal the threads of the polar capsules are extruded, fixing the little 

 spore, which bursts and allows the amoeboid sporozoite to escape and go on 

 its travels in search of a suitable tissue. Perhaps en route it conjugates with 

 another sporozoite; if so, this is not known. While sporogony is preparing, 

 schizogony may take place by plasmotomy, which is the division of the multi- 

 nuclear trophozoite into two or more forms. 



It will thus be seen that growth, plasmotomy (schizogony), and spore- 

 formation (sporogony) go on simultaneously. 



Classification. — Disporea Doflein, 1899. — Phaenocystes with two spores. 



Family, — Cer atomy xidcs Doflein, 1901. 



Genera, — Ceratomyxia, Leptotheca. — Parasitic in fish and frogs. 

 Polysporea Doflein, 1899. — Phaenocystes with more than two spores. 



Family i. — Myxidiidcs Auerbach, 1910. 

 Genera. — Sphcerospova, Myxidium. 



Family 2. — ChloyomyxidcB Thelohan. 



Family 3. — Myxobolidcs Gurley, 1893. 



SUBORDER II. CRYPTOCYSTES. 



This order is divided by Doflein and Perez into : — 



Tribe i. Monosporogenea Perez. — Trophozoite becomes a single pansporo- 

 blast (sporont), which produces a single spore. 



Tribe 2. Oligosporogenea Doflein, 1899. — Trophozoite becomes a single 

 pansporoblast (sporont), which produces four to eight spores. 



Tribe 3. Polysporogenea Doflein, 1899. — Trophozoite becomes numerous 

 pansporoblasts (sporont), which produce many spores. 



Tribe i. Monosporogenea. 



This tribe includes Nosema bombycis Nageli, 1857, which is the cause of 

 pebrine, the silkworm disease. N. apis Zander, 1909, was shown to be the 

 cause of microsporidiosis in bees in England by Fantham and Porter. 



Tribe 2. Oligosporogenea Doflein, 1899. 



This includes the genera Gurleya Doflein, Thelohania Henneguy, and Pleisto- 

 phora Gurley. 



Tribe 3. Polysporogenea Doflein, 1899. 



This includes the genera of Glugea Thelohan, and Myxocystes Mrazek, of 

 which Glugea anomala Moniez is a parasite of the stickleback. 



Microsporidium polyedricum Bolle, a doubtful species, is said by Perroncito 

 to occur in man. 



ORDER II. ACTINOMYXIDIA Stole, 1899. 



These are parasites in the Tubificidse of the oligochaete worms, and need not 

 concern us. 



34 



