The Telosporidia comprise the Gregarinida, the Coccidiidea, and the Hæmosporidia. Doflein combines the two latter orders into one known as the Coccidiomorpha.
The Neosporidia comprise the Myxosporidia, the Microsporidia, the Actinomyxidia, the Sarcosporidia, and the Haplosporidia. Doflein combines the first three orders into one, the Cnidosporidia.
Sub-Class. TELOSPORIDIA, Schaudinn.
Sporozoa in which the reproductive phases follow completion of growth.
Order. Gregarinida, Aimé Schneider emend. Doflein.
Fig. 59.—Monocystis agilis from seminal vesicles of Lumbricus × 250. (After Stein.)
Knowledge of the Gregarinida probably goes back as far as the year 1684, when Redi observed gregarines in the crab, Cancer pagurus. Von Cavolini (1787) found them in Cancer depressus. The name Gregarina was created by L. Dufour (1828), who observed masses of these organisms in the gut of insects of different orders. Hammerschmidt (1838) and von Siebold found rich infestations in insects, while Dujardin (1835) and Henle described various genera from segmented worms. Henle (1835) also observed cysts containing “navicellæ” in the sperm-sacs of segmented worms, and attention was drawn to his researches by the discovery by von Siebold (1839) of “pseudonavicellæ” in the gut of Sciara nitidicollis. Up to this time many workers considered the gregarines to be worms, but Kölliker (1845) investigated many of them and maintained their unicellular nature, while Stein’s work (1848) showed the interrelation of the pseudonavicellæ and the gregarines. The discovery of amœboid germs in the pseudonavicellæ by Lieberkühn (1855) and the demonstration of myonemes further aided in the elucidation of their true systematic position. The entire process of conjugation, of which Dufour had seen one phase, was followed by Giard under the microscope.
From 1873 onwards Aimé Schneider made important additions to the knowledge of the morphology, life-history, and systematic position of numerous gregarines. Bütschli (1881) and L. Léger (1892) also contributed much work on the subject. The discoveries of Schaudinn with regard to the life-cycle of Coccidia gave a fresh stimulus to the study of the Gregarines, whereby the life-cycles of numerous forms and the phases thereof have been elucidated.