92 E. RAY LANKESTER, ON GREGARINIDE. 
Genus. Gregarina; two animals frequently hanging 
together. 
Family. Didymophy idez ; body divided into three parts by 
two septa. 
Genus. Didymophyes ; characters of the family. 
Of this classification Professor Greene* remarks—“ This, 
however, is an arbitrary division, and if not erroneous, is 
certainly premature.’ Certain of the genera proposed by 
Stein are, without doubt, objectionable; thus, the genus 
Zygocistis is based upon a habit of the species, namely, that 
of adhering together, which is only occasional, and is com- 
mon to all “Gregarinz when about to become encysted. The 
fact of certain Gregarine being provided with anterior ap- 
pendages is not sufficient to constitute a genus, inasmuch as 
certain species which usually present the characters of the 
genus Sporadina have occasionally been found with a well- 
developed appendix to the cephalic sac.t Similar objections 
may be raised against the genera Actinocephalus and Gre- 
garina. Dr. C. M. Diesing, ae his ‘ Systema Helminthum,’t 
has given a complete list of species known at that time, with 
descriptions of some new species from Crustacea, and has 
supplemented this by a further catalogue of species in the 
‘ Sitzungsberichte der Academie der Wissenschaften,’ 1859. 
The existence of a double membrane, and its peculiar modifi- 
cation into a prehensile or absorbent organ, certainly does ap- 
pear to raise certain Gregarine above the Protozoa; their true 
position in the scale of nature is by no means yet satisfactorily 
decided. He places the Gregarinidz among the Helmintha rhyn- 
godea, considering the proboscidiform appendage with which 
some Gregarine are furnished, as a suctorial apparatus. He 
enumerates seventy-five species, but many of these require fur- 
ther investigation before they can be admitted as distinct from 
other forms with which they are associated. Dr. A. Schmidt, 
in ‘ Abhandl. d. Senkenberg’schen Gesellschaft,’ 1, 1854, has 
described several varieties of Gregarinz from the earthworm. 
Schultze, Girsted, and others have described species of Gre- 
garin; reference to their works will be found in the biblio- 
graphy at the end of this paper. In the following list of 
species I have modified Stein’s classification, and suppressed 
some of the species which appear to be mere varieties. I have 
also given the names under which the species were originally 
described, Diesing having attempted to alter them consider- 
* «Manual of the Protozoa,’ p. 51. 
i Leidy, loc. cit. 
t Vol. ii, p. 6, &c., Vindobone, 1851. 
