PROTO/OA OU SlMl'LKS'I' ANIMALS. 



14. 



Jl 



or tissues. Mention m:iy conveniently be made here, ulso, of Sleeping 

 Sickness and Tsetse disease, caused by the presence in the bl<j<Ml. 

 respectively of man and of domestic animals, of a parasite {Try- 

 panosoma) belongini? to the Flagellata antl allied t<t the Sporozoa. 



General Chauactehs of the Oiioui'. 

 The Sporozoa, from their i)arasitic habit of Fig. ioa. 



passively absorbing the juices of their Ixjst, lack JUSt^ 



organs for capturing and digesting food. Usually 

 they are of more or less deiinite form, and with 

 the cell body bounded by a cuticle. Generally 

 they are stationary, though some move by means 

 of pseudopods (like Amocbixi), and some have 

 flagella during a phase of their life cycle. The 

 most important cliaracter, and the one to which 

 the group owes its name, is that of forming 

 spores or germs, which arc commonly enclosed 

 each in a tough envelope or cyst (Fig. 10b), and 

 often all the spores formed from one parent cell 

 are enclosed in a common cyst. Tiie conditions 

 necessary for the existence of these organisms are 

 so nicely adjusted that each species of parasite is 

 usually confined to the same or an allied species 

 of host, and to the same tissues of that host. 



The Sporozoa may be grouped under the fol- 

 lowing headings : — (1) Gregarines, (2) Coccidia, 

 (8) Myxosporidia and Sarcosporidia, and (4) Para- 

 sites of the blood. 



(1) Gregarines. These organisms are of very 

 common occurrence in the intestine and body 

 cavity of invertebrate animals. 



Porospora gigantea (Fig. Ioa), from the 

 intestine of the lobster, is an unusally large 

 species. Specimens, which may be nearly an inch 

 in length, look like small worms, yet in spit*.' of 

 such huge dimensions they consist of only a 

 single cell with a nucleus. The cell 1)ody in 

 this and some other species is divided into two 

 segments, the upper one Ijeing small and often (After "an 

 modified so as to become an efficient fixing organ. from Lm; 



MonocijHtis Of/ilis is very commonly found \\ ithin the spenu siws 

 of earth worms. The little elongated oval Gregarine lives in it.s 



II 



/J 



Porosjwra fiitianUa, 



X 150.' 



from intostino of 



Lobster. 



