ORIGINAL COMMUNICATIONS. 
On our Present Know ence: of the GREGARINIDA, with 
DescrirTions oF THREE New Species belonging to that 
class. By HK. Ray LanKester. 
In Vol. I. of this Journal (1853), p. 211, an abstract ap- 
peared of some observations made by Kolliker and others 
on the Gregarinide, a group of animals of very simple struc- 
ture, met with in the intestine and other parts of many in- 
sects and annelids, the nature of which was then, and is 
still, a matter of considerable interest to naturalists. Others 
have worked at the subject since that time, but little has 
been published in England relating to these parasites, nor 
are they generally known to microscopic observers in this 
country. It may, therefore, be advantageous to give in a 
condensed form what is known of their structure and de- 
velopment, adding a list of species and a few original obser- 
vations. 
In 1837, Léon Dufour* described a group of microscopic . 
organisms, which he discovered in the interior of several 
species of insects, under the name of Gregarina, “ qu’exprime 
VPhabitude qu’ont ces Entozoaires de vivre par troupeaux.” 
He had before remarked upon their occurrence,t but with- 
out fully describmg or naming them. Here he describes 
them as possessing a mouth and composed of two membranes, 
the internal one enclosing a clear fluid. Later researches 
have shown Dufour’s description to be partially erroneous. 
The Gregarine vary considerably in form, being, in most 
cases, more or less ovate. In those found in insects and 
crustacea the body is unequally divided by internal septa 
into two segments, which have been called respectively the 
anterior and posterior sacs. In some species three such 
divisions have been observed. Other forms met with in 
Annellida have no internal septa, but are unilocular. In 
* «Ann. des Sci. Nat.,’ tome vii, 1837, p. 10. 
+ Ibid., tome viii, lre séries, xiii. 
VOL. III.—NEW SER. G 
