216] The Classification of Lower Organisms 



The genus which is best known is Monocystis Stein, including several species which 

 are common in earthworms. The cells grow within epithelial cells of the seminal fun- 

 nels; they and their nuclei reach considerable sizes without dividing. At maturity, 

 they escape into the seminal vescicles, where they form pairs, each pair secreting a 

 common cyst wall. The pairing and encystment were observed, more definitely of the 

 related genus Zygocystis than of Monocystis, by Stein (1848). The nuclei of the 

 paired cells divide. Several observers, as Brasil (1905) and Mulsow (1911); also, as 

 to related genera, Jameson (1920) and Noble (1938); have observed peculiarities in 

 the first nuclear division. The peculiarities amount to this, that the large nucleus 

 breaks up and, for the most part, undergoes dissolution, leaving a small number of 

 definite chromosomes to undergo normal mitosis in a spindle. Repeated subsequent 

 divisions are of normal character. The numerous nuclei thus produced become those 

 of gametes which are budded oflF from the surfaces of the gametocytes. This was first 

 observed by Wolters (1891). The gametes from the respective paired cells are pre- 

 sumably always of different mating types, and are usually visibly differentiated, 

 larger and smaller. Each zygote becomes a spindle-shaped walled spore; the enucleate 

 remainder of the gametocytes provides nourishment during their development. Each 

 spore produces eight sporozoites. 



The number of known species of Monocystidea is of the order of 150. The majority 

 occur in annelid worms; others attack flatworms, echinoderms, insects, tunicates, and 

 other invertebrates. Bhatia (1930) distinguished twelve famiHes which are here 

 merely listed. 



A. The two ends of the spore alike. 



Family 1. Monocystida [Monocystidae] (Biitschli) Poche in Arch. Prot. 30: 236 

 (1913). Family Monocystiden Stein in Arch. Anat. Phys. 1848: 187 (1848). Mono- 

 cystidae Biitschli ( 1882). Monocystis, etc. 



Family 2. Rhynchocystida [Rhynchocystidae] Bhatia in Parasitology 22: 158 

 (1930). Rhynchocystis. 



Family 3. Stomatophorida [Stomatophoridae] Bhatia op. cit. 159. Stomatophora, 

 Choanocystis, etc. 



Family 4. Zygocystida [Zygocystidae] Bhatia op. cit. 160. Zygocystis, Pleurocystis. 



Family 5. Akinetocystida [Akinetocystidae] Bhatia op. cit. 160. Akinetocystis. 



Family 6. Syncystida [Syncystidae] Bhatia op. cit. 161. Syncystis. 



Family 7. Diplocystida [Diplocystidae] Bhatia op. cit. 161. Diplocystis, Lankcsteria. 



Family 8. Schaudinellida [Schaudinellidae] Poche in Arch. Prot.' 30: 236 (1913). 

 Schaudinella. 



B. The ends of the spores differentiated. 



Family 9. Doliocystida [Doliocystidae] Labbe in Thierreich 5: 33 (1899). Family 

 Lecudinidae Kamm. Lxcndina Mingazzini {Doliocystis Legcr). 



Family 10. Urosporida [Urosporidae] Woodcock 1906. Family Choanosporidae 

 Dogiel. Gonospora; Lithocystis; Urospora, the spores with long tails; Ceratospora; 

 Pterospora, the spores with longitudinal flanges. 



Family 11. Ganymedida [Ganymcdidae] J. S. Iluxlcy in Quart. Jour. Micr. Sci. 

 n..s. 55: 169 (1910). Ganymcdcs. 



Family 12. Allantocystidae [Allantocystidae] Bhatia op. cit. 163. Allantocystis. 



Order 7. Polycystidea Biitschli in Bronn Kl. u. Ord. Thicrreichs 1: 578 (1882). 

 Order Grcgarinae Haeckel Gen. Morph. 2: xxv (1866), the mere plural of a 

 generic name. 



