Schizogony very exceptional, only occurring during the intracellular
phase, if at all. Gregarines fall naturally into two tribes, described
as cephalont and septate, or as acephalont and aseptate (haplocytic),
respectively. In strictness, however, as already mentioned, these two
sets of terms do not agree absolutely, and whichever set is adopted,
the other must be taken into account in estimating the proper position
of certain parasites. Here the cephalont or acephalont condition is
regarded as the more primary and fundamental.
Tribe A.--_Cephalina_ (practically equivalent to _Septata_).
Save exceptionally, the body possesses an epimerite, at any rate
during the early stages of growth, and is typically septate. Mostly
intestinal parasites of Arthropods.
The chief families, with representative genera, are as follows:
_Porosporidae_, with _Porospora gigantea_, at present thought to be
gymnosporous; _Gregarinidae_ (_Clepsydrinidae_), with _Gregarina_,
_Clepsydrina_, _Eirmocystis_, _Hyalospora_, _Cmenidospora_,
_Stenophora_; _Didymophyidae_, with _Didymophyes_; _Dactylophoridae_,
with _Dactylophorus_, _Pterocephalus_, _Echinomera_, _Rhopalonia_;
_Actinocephalidae_ with _Actinocephalus_, _Pyxinia_, _Coleorhynchus_,
_Stephanophora_, _Legeria_, _Stictospora_, _Pileocephalus_,
_Sciadophora_; _Acanthosporidae_ with _Acanthospora_, _Corycella_,
_Cometoides_; _Menosporidae_ with _Menospora_, _Hoplorhynchus_;
_Stylorhynchidae_, with _Stylorhynchus_, _Lophocephalus_;
_Doliocystidae_ with _Doliocystis_; and _Taeniocystidae_, with
_Taeniocystis_. The curious genus _Selenidium_ is somewhat apart.
Tribe B.--_Acephalina_ (practically equivalent to _Aseptata_,
_Haplocyta_).
The body never possesses an epimerite and is non-septate. Chiefly
coelomic parasites of "worms," Holothurians and insects.
The _Aseptata_ have not been so completely arranged in families as the
_Septata_. Leger has distinguished two well-marked ones, but the
remaining genera still want classifying more in detail. Fam.
_Gonosporidae_, with _Gonospora_, _Diplodina_; and _Urosporidae_, with
_Urosopora_, _Cystobia_, _Lithocystis_, _Ceratospora_; the genera
_Monocystis_, _Diplocystis Lankesteria_ and _Zygocystis_ probably
constitute another; _Pterospora_ and, again, _Syncystis_ are distinct;
lastly, certain forms, e.g. _Zygosoma_, _Anchora_ (_Anchorina_), are
incompletely known.
There remains for mention the remarkable parasite, recently described
by J. Nusbaum (24) under the appropriate name of _Schaudinnella
henleae_, which inhabits the intestine of _Henlea leptodera_. Briefly
enumerated, the principal features in the life-cycle are as follows.
The young trophozoites (aseptate) are attached to the intestinal
cells, but practically entirely extracellular. Association is very
primitive in character and indiscriminate; it takes place
indifferently between individuals which will give rise to gametes of
the same or opposite sex. Often it is only temporary; at other times
it is multiple, several adults becoming more or less enclosed in a
gelatinous investment. Nevertheless, in no case does true encystment
occur, the sex-cells being developed practically free. The female
gametes are large and egg-like; the males, minute and sickle-like, but
with no flagellum and apparently non-motile. While many of the zygotes
("amphionts") resulting from copulation pass out to the exterior, to
infect a new host, others, possessing a more delicate
investing-membrane, penetrate in between the intestinal cells,
producing a further infection (auto-infection). Numerous sporozoites
are formed in each zygote. It will be seen that _Schaudinnella_ is a
practically unique form. While, on the one hand, it recalls the
Gregarines in many ways, on the other hand it differs widely from them
in several characteristic features, being primitive in some respects,
but highly specialized in others, so that it cannot be properly
included in the order. _Schaudinnella_ rather represents a primitive
Ectosporan parasite, which has proceeded upon a line of its own,
intermediate between the Gregarines and Coccidia.
BIBLIOGRAPHY.--Among the important papers relating to Gregarines are
the following: 1. A. Berndt, "Beitrag zur Kenntnis der ...
Gregarinen," _Arch. Protistenk._ I, p. 375, 3 pls. (1902); 2. L.
Brasil, "Recherches sur la reproduction des Gregarines monocystidees,"
_Arch. zool. exp._ (4) 3, p. 17, pl. 2 (1905), and _op. cit._ 4, p.
69, 2 pls. (1905); 3. L. Brazil, "_Eleutheroschizon duboscqi_,
parasite nouveau, &c.," _op. cit._ (N. et R.) (4), p. xvii., 5 figs.
(1906); 4. M. Caullery and F. Mesnil, "Sur une Gregarine ...
presentant ... une phase de multiplication asporulee," _C.R. Ac. Sci._
126, p. 262 (1898); 5. M. Caullery and F. Mesnil, "Le Parasitisme
intracellulaire des Gregarines," _op. cit._ 132, p. 220 (1901); 6. M.
Caullery and F. Mesnil, "Sur une mode particuliere de division
nucleaire chez les Gregarines," _Arch. anat. microsc._ 3, p. 146, 1
pl. (1900); 7. M. Caullery and F. Mesnil, "Sur quelques parasites
internes des Annelides," _Misc. biol._ (_Trav. Stat. Wimereux_), 9, p.
80, 1 pl. (1899); 7a. J. Cecconi, "Sur l'_Anchorina sagittata_, &c.,"
_Arch. Protistenk._ 6, p. 230, 2 pls. (1905); 8. H. Crawley,
"Progressive Movement of Gregarines," _P. Ac. Philad._ 54, p. 4, 2
pls. (1902), also _op. cit._ 57, p. 89 (1905); 9. H. Crawley, "List of
the Polycystid Gregarines of the U.S.," _op. cit._ 55, pp. 41, 632, 4
pls. (1903); 10. L. Cuenot, "Recherches sur l'evolution et la
conjugaison des Gregarines," _Arch. biol._ 17, p. 581, 4 pls. (1901);
11. A. Laveran and F. Mesnil, "Sur quelques particularites de
l'evolution d'une Gregarine et la reaction de la cellule-hote," _C.R.
Soc. Biol._ 52, p. 554, 9 figs. (1900); 12. L. Leger, "Recherches sur
les Gregarines," _Tabl. zool._ 3, p. i., 22 pls. (1892); 13. L. Leger,
"Contribution a la connaissance des Sporozoaires, &c.," _Bull. Sci.
France_, 30, p. 240, 3 pls. (1897); 14. L. Leger, "Sur un nouveau
Sporozoaire (_Schizocystis_), &c.," _C.R. Ac. Sci._ 131, p. 722
(1900); 15. L. Leger, "La Reproduction sexuee chez les Ophryocystis,"
_t. c._ p. 761 (1900); 16. L. Leger, "Sur une nouvelle Gregarine
(_Aggregata coelomica_,), &c." _op. cit._ 132, p. 1343 (1901); 17. L.
Leger, "La Reproduction sexuee chez les Stylorhynchus," _Arch.
Protistenk._ 3, p. 304, 2 pls. (1904); 18. L. Leger, "Etude sur
_Taeniocystis mira_ (Leger), &c.," _op. cit._ 7, p. 307, 2 pls.
(1906); 19. L. Leger and O. Duboscq, "La Reproduction sexuee chez
_Pterocephalus_," _Arch. zool. exp._ (N. et R.) (4) 1, p. 141, 11
figs. (1903); 20. L. Leger and O. Duboscq, "_Aggregata vagans_, n.
sp., &c." _t. c._ p. 147, 6 figs. (1903); 21. L. Leger and O. Duboscq,
"Les Gregarines et l'epithelium intestinal, &c.," _Arch. parasitol._
6, p. 377, 4 pls. (1902); 22. L. Leger and O. Duboscq, "Nouvelles
Recherches sur les Gregarines, &c.," _Arch. Protistenk._ 4, p. 335, 2
pls. (1904); 23. M. Luhe, "Bau und Entwickelung der Gregarinen," _t.
c._ p. 88, several figs. (1904); 24. J. Nusbaum, "Uber die ...
Fortpflanzung einer ... Gregarine, _Schaudinnella henleae_," _Zeit.
wiss. Zool._ 75, p. 281, pl. 22 (1903); 25. F. Paehler, "Uber die
Morphologie, Fortpflanzung ... von _Gregarina ovata_," _Arch.
Protistenk._ 4, p. 64, 2 pls. (1904); 26. S. Prowazek, "Zur
Entwickelung der Gregarinen," _op. cit._, 1, p. 297, pl. 9 (1902); 27.
A. Schneider (Various memoirs on Gregarines), _Tabl. zool._ 1 and 2
(1886-1892); 28. H. Schnitzler, "Uber die Fortpflanzung von
_Clepsydrina ovata_," _Arch. Protistenk._ 6, p. 309, 2 pls. (1905);
29. M. Siedlecki, "Uber die geschlechtliche Vermehrung der _Monocystis
ascidiae_," _Bull. Ac. Cracovie_, p. 515, 2 pls. (1900); 30. M.
Siedlecki, "Contribution a l'etude des changements cellulaires
provoquees par les Gregarines," _Arch. anat. microsc._ 4, p. 87, 9
figs. (1901); 31. H. M. Woodcock, "The Life-Cycle of _Cystobia
irregularis_, &c.," _Q.J.M. Sci._ 50, p. 1. 6 pls. (1906).
(H. M. Wo.)