191(3.] NATURAL SCIENCES OF PHILADELPHIA. 387 



Subclass II, Neosporidia. 



Order 1, Cnidosporidia. 



Suborder A, Myxosporidia. 



Suborder B, Microsporidia. 



Suborder C, Actinomyxidia. 

 Order 2, Haplosporidia. 



It is to be observed that the characters used by Doflein to classify 

 the Telosporidia are not those having to do with the nature of the 

 life history. Thus, although the Haemosporidia have two host- 

 while the Coccidia have but one, these two groups are ranked ;i- 

 closely related suborders. Therefore the fact that we are still in the 

 dark as to whether the Sarcosporidia have two hosts or only one has 

 no bearing upon what is their proper place in the classification of the 

 Sporozoa. 



With regard to this question, the probabilities are that there are 

 two hosts. Indeed, such an hypothesis is more or less obligatory 

 when it comes to accounting for the wide-spread occurrence of 

 Sarcosporidia in purely herbivorous animals, such as sheep. As no 

 more than an interesting speculation, it might be suggested that the 

 second host, a carnivor, infects itself by eating the infected flesh of 

 a herbivor. The merozoites, released in the intestine, initiate the 

 sexual cycle and the encysted form is discharged in the feces. This 

 encysted stage, ingested by a herbivor with its food, eventual ly 

 infects the muscles and the cycle is repeated. Analogy would lead 

 us to suspect that the sexual cycle is, in general, confined to the 

 carnivor; the asexual to the herbivor. This view receives a certain 

 amount of indirect support from the facts that whereas the purely 

 herbivorous sheep and cattle are practically invariably infected, 

 records of the finding of sarcosporidian cysts in the muscles of car- 

 nivorous animals are very rare. Finally, the fact that in the mouse 

 both the sexual and asexual cycles occur presents no particular 

 difficulty. Mice are omnivorous and can infect themselves either 

 by eating the flesh of their dead fellows, or, as Negre first showed. 

 by the contamination of their food with the encysted fecal stage. 

 In conclusion, it may be mentioned that Negre's discovery is of 

 the utmost significance when it comes to an endeavor to elucidate 

 the life history of the Sarcosporidia. Yet, for whatever may have 

 been the reasons, it has been persistently overlooked or ignored and 

 hence has never been awarded the credit to which it is entitled. 



