20 Protozoan Parasite. 



Nature of tlic Parasites. — At first sight one is struck by the 

 similarity to colonies of Herpetomonas and to certain stages of 

 the Malaria-parasite in Anopheles, but there is no evidence 

 'ivhatever of a blepharoplast or centrosome. 



Dr. Mesnil, of the Pasteur Institute, Paris, to whom I 

 forwarded a section for his opinion, agrees with this, but con- 

 siders the resemblance much greater to certain stages of para- 

 sites of the intestines of some crustaceans, known as Aggregata. 

 Indeed, he states that on comparing the two, " the resemblance 

 is striking." As he suggests, it is more than possible that the 

 parasite in question is a schizogonic stage in the evolution of 

 some parasitic sporozoon of the sheep. Now as there is one 

 sporozoon which is extremely common in my experience, not 

 only in the sheep, but in cattle and pigs in Australia — viz., the 

 sarcosporidium, the life history of which is extremely obscure, 

 the possibility of its being a stage in its evolution is worthy 

 of consideration. In almost every portion of muscle which I 

 have examined microscopically in Australia, I have found some 

 fibres affected with sarcosporidia. Their further study is there- 

 fore a matter of some economic as well of scientific import- 

 ance. Unfortuntely, the minute size of the stomach cyst renders 

 an investigation into the parasite mentioned a matter of 

 extreme difficulty, but it should not be unsurmountable. 



EXPLANATION OF PLATE HI. 



Upper Figure. — Section of stomach mucosa, showing cyst. 

 Lower Figure. — -Groups of Sporozoites showing radiate arrange- 

 ment. 



Postscript, 7th July. 



It is interesting to note that iii a private communication 

 received from Dr. Mesnil since the above article was read, he 

 states that the cysts have now been found to exist in the fourth 

 stomach of sheep slaughtered in the Paris abattoirs. His 

 assistant, M. Chatton has made a very complete study of them, 

 which will be published shortly. 



