GEEGARIXID.E. 51 



The partition by which the two Gregarince were 

 at first separated meanwhile disappears, the cyst 

 bursts, and the pseudonaviculae escaping therefrom 

 burst in their turn, and give rise to amoebiform 

 bodies which at length develope themselves into 

 young Gregarinidce, But the coalescence of two 

 Gregarinidce is by no means a necessary prelimi- 

 nary to the formation of pseudonaviculae, since 

 these are sometimes observed to occur within the 

 bodies of single animals. 



4. Classification. — The Gregarinidce have 

 been divided by Stein into three sections, viz. : — 



1. MonocystidecB. — Simple Grregarinidse without 



constrictions or internal septa. 



2. Gregarmarice. — Gregarinidse with the body 



divided into two portions. 



3. Didimophydce. — Gregarinidse with the body 



divided into three parts, as if resulting fi-om 

 the adhesion of two individuals, one from each 

 of the preceding sections. 



This, however, is merely an arbitrary division, 

 and, if not erroneous, is certainly premature. 



By some the Gregarinidce have been regarded 

 as vegetable forms ; by others, as larval stages of 

 various Annuloida, Neither of these opinions has 

 been supported by proofs, and, upon the whole, it 

 seems desirable, for the present at least, to view 

 these organisms as adult members of the sub- 

 kingdom Protozoa, 



5. Psorosperniiee. — The Psorosperonice are 

 exceedingly minute parasitic creatures, occurring 

 in great numbers both on and within the bodies 

 of fishes. In form they are ovate, hemispherical, 



E 2 



