156 MANUAL OF ELEMENTARY ZOOLOGY 



In comparing this life-history with that of Monocystis 

 some important differences appear, (a) In Monocystis the 

 trophozoite is not amoeboid, eventually outgrows its cell- 

 host, and does not reproduce asexually {i.e., does not become 

 a meront) ; (b) in the malaria parasite the gametes are 

 much more unlike than in Monocystis and the female 

 gamont gives rise only to one gamete; (c) in Monocystis 

 there is no sporoblast generation between the zygote and 

 the sporozoites ; (d) in Monocystis there is probably no 

 necessity for a second kind of host, sexual reproduction and 

 the division of the zygote both take place in the host in 

 which the parent trophozoites live, and the zygote-cyst (the 

 pseudonavicella) does not burst and set free the sporozoites 

 until it reaches the host in which the new generation of 

 trophozoites are to live. The whole process is more highly 

 developed in the malaria parasite. 



Malaria is very widely distributed. It is found in 

 tropical and subtropical lands of every quarter of the globe 

 and even in such temperate countries as England, where it 

 still lingers in marshy districts in the form of ague, once 

 much more prevalent than now. The parasites which 

 cause it are always transmitted by the Anopheline Flies 

 or "Mosquitoes," being incapable of harbouring in the 

 related Culicine Flies or " Gnats," which digest the game- 

 tocytes. 



Gnats and mosquitoes, though they are much alike to 

 the untrained eye, may be distinguished by sundry small 

 differences, notably by the carriage of the body in the 

 resting position (Fig. 97). Both these kinds of flies lay 

 their eggs in water, and there pass through larval and pupal 

 stages (pp. 284, 285). It is practically hopeless to attempt 

 to destroy the adults on a large scale, but they may often 

 be prevented from breeding by doing away with all suitable 

 pieces of water, or attacking the young stages by pouring 

 paraffin over the breeding-places, introducing fish which 

 feed upon them, and so forth. 



The loss of time, energy, and life itself from this disease 

 is very serious in many warm countries, notably, for 

 instance, on the West Coast of Africa. Formerly quinine 

 was almost the only resource against it, but the discovery 

 of the parasite and its life-history — a romance of Science, 



