THE SPOROZOA 153 



anatomist Redi (1708), but his claims to this honour are very doubtful. 1 

 Cavolini, however, in 1787, described and figured an indubitable Gregarine 

 (Aggregata conformis (Dies.), fide Labbe") from the glandular appendages 

 of the stomach of Pachygrapsus marmoratus. He found conjugating 

 individuals, and believed each such pair to be a kind of tapeworm with 

 two segments. But the true discoverer of the group, in the scientific 

 sense, was Le"on Dufour, who, in his researches upon insect -anatomy, 

 became acquainted with, and described, numerous species of these parasites. 

 He regarded them as a peculiar group of worms, allied to Trematodes, to 

 which in 1828 he gave the generic name Gregarina. More species were 

 subsequently made known by other authors, and in 1839 Siebold published 

 an important work in which he described the nucleus accurately for the 

 first time, without, however, recognising the true nature of Gregarines, 

 which he also considered as worms, though he did not attribute to them 

 an alimentary canal, as had been done by one of his predecessors ! Siebold 

 also described the cysts and spores found associated with the Gregarines, 

 and though he did not discover the connection between them, his observa- 

 tions had the merit of drawing attention to the " pseudonavicellae " already 

 observed by Henle (1835) and others in the sperm-sacs of the earth- 

 worm. 



Contemporaneously with Siebold's work appeared the investigations of 

 Hake upon the spores of the Coccidium of the rabbit, which, however, the 

 author regarded as pathological products of the tissues of the host itself. 

 In 1841 the celebrated Johannes Muller described the spores of a number 

 of different Myxosporidia inhabiting various fishes, and termed these 

 organisms "psorosperms," 2 a name of very frequent occurrence in sporozoan 

 literature, applied to various kinds of spores. Muller was, however, quite 

 in the dark as to the nature of his psorosperms, and considered them a 

 "living seminium morbi" comparable to spermatozoa. After Muller 

 psorosperms were studied by many observers, and generally divided into 

 "egg-shaped psorosperms," e.g. Coccidia, and " fish - psorosperms " or 

 " Miiller's psorosperms," the spores of Myxosporidia. Their affinities 

 remained, however, uncertain for a very long time, and indeed the true 

 nature of " fish-psorosperms " has only been elucidated completely in the 

 most recent times. As long ago as 1842 Creplin compared psorosperms 

 to pseudonavicellae, and so laid the foundation of the " Gregarine-theory " 

 of the Myxosporidia. But this comparison was not universally accepted, 

 although supported by Leydig, Lieberkiihn, and other observers. Many 

 authors, on the other hand, regarded psorosperms as organisms of a 

 vegetable nature, allied to Diatoms. 



A distinct epoch in our knowledge of the Sporozoa was made by 

 Kolliker, who in 1845 and 1848 not only greatly increased our know- 

 ledge of these parasites, and of their wide distribution and occurrence in 

 hosts of all classes, but further expressed and maintained for the first time 

 the opinion that Gregarines were unicellular organisms, which should be 



1 See Biitschli, " Sporozoa " in Bronn's Thierreich, i. p. 480, from whom most of 

 the historical facts here put together are taken. Labbe [4] identifies the Gregarine 

 figured by Redi as Aggregata praemorsa (Dies.). 



2 Derived, according to Balbiani, from \f/upa, mange, and crir^yia, seed. 



