INTRODUCTION 



21 



by Ehrenberg, but curiously misinterpreted as ciliated forms (a mis- 

 take rectified only during the last twenty years), which led Clapa- 

 rede and Lachmann('58), R. S. Bergh ('84), and Saville Kent ('81) to 

 regard these organisms, under the name Cilio-flagellata, as inter- 

 mediate forms between the Ciliata and the Mastigophora ; (3) Cysto- 

 flagellidia (Haeckel), including two genera, Noctiluca and Leptodiscus, 

 the former observed during the eighteenth century, the latter dis- 

 covered by R. Hertwig ('77). 



Fig. 7. Two forms assumed by Leptotheca agilis, a myxospore. [DOFLEIN.] 



The history of the Sporozoa as a class dates from Kblliker's ('45- 

 '48) and Stein's ('48) works, although the name Gregarine now used 

 as the title of an order (Gregarinida) goes back to Leon Dufour 

 ('28), and the first observation to Redi in the seventeenth century. 1 

 The different kinds of Sporozoa were first grouped together by 

 Leuckart ('79) under the present name, and he subdivided the group 

 into the Gregarinida (Fig. I, D) and the Coccidiida (Fig. 6), the 

 former dwelling in cavities of various invertebrate hosts, t the latter 

 inside epithelial cells in, chiefly, vertebrate hosts. Under the term 

 psorosperms (Joh. Muller, '41), a number of fish parasites belong- 

 ing to the Sporozoa were known early in the century, and 

 these were grouped together by Biitschli under the term Myxospo- 



1 Cf. Diesing, p. 183. 



