THE SPOROZOA: II. THE HJEMOSPORIDIA 



IN the order Haemosporidia are comprised a number of organisms 

 characterized by the following peculiarities : They are parasites of 

 the blood-corpuscles, red or white, of vertebrates during a part of 

 the life-cycle ; like the Coccidia, they exhibit an alternation of 

 generations, non-sexual schizogony and sexual sporogony ; and, in 

 all cases thoroughly investigated up to the present, the alternation 

 of generations corresponds to an alternation of hosts, the schizogony 

 taking plaee in the blood or internal organs of a vertebrate, the 

 sporogony in the digestive tract or other organs of an invertebrate ; 

 lastly, resistant spores are not, as a rule, produced in this order, 

 being rendered unnecessary by the fact that the parasite is never, 

 so to speak, in the open, but always sheltered within the body of 

 one or the other of its two hosts during its entire life-cycle. 



The Haemosporidia, as the name is generally understood, are a 

 group which comprises a number of forms differing considerably 

 amongst themselves. Some of the types referred at present to 

 this order will, perhaps, when thoroughly investigated, be removed 

 from the order altogether. The existence of these dubious forms 

 renders the precise limits of the group uncertain and ill-defined. 

 All that can be said at present is that the order contains a nucleus 

 of true Haemosporidia presenting very obvious and close affinities 

 with the Coccidia, and, in addition to such forms, certain others, 

 the true affinities of which remain to be determined, but which can 

 be ranked provisionally in the group. 



Under these circumstances, the occasion is not yet ripe for treating 

 the group in a comprehensive manner, as has been done with 

 Gregarines and Coccidia. The difficulty of dealing with these 

 blood-parasites is enhanced by the fact that there is perhaps no 

 group in the animal kingdom in which the nomenclature-purist has 

 wrought such havoc as in the Haemosporidia. Matters have reached 

 such a pitch that in some cases the popular names of certain forms 

 are more distinctive than their strictly scientific appellations, so 

 that the very raison d'etre of a scientific terminology has been 



stultified. 



356 



