MICROSPORIDIA 531 



E. sanguineus in India, and Dermacentor reticulatus in Europe. 1 

 (On Ticks, see Nuttall, Journ. Eoy. Inst. of Public Health, vol. xvi, 

 1908, p. 385.) 



H aemogregarina 



The Hsemogregarines (which must be distinguished from the 

 Gregarines) are unpigmented parasites, not amoeboid, typically 

 having an elongated body or vermicule, occurring in the blood, 

 mostly in cold-blooded vertebrates, but several species have of 

 late been found in mammals (dog, jerboa, palm squirrel), though 

 not in man. In the dog, the parasite (Leucocytozoon canis) occurs 

 as an elongated, curved or doubled-up body in the polymorphonu- 

 clear leucocytes. It is encapsuled and contains a single granular 

 nucleus. Encystment with sporulation occurs in the bone -marrow, 

 and a sexual development is stated to occur in a tick. 



Hcemogregarina (Drepanidium, Lankesterella) ranarum inhabits 

 frogs (Eana esculenta), and possesses both an intra- and an extra- 

 corpuscular phase. In the former the parasite occurs as an elon- 

 gated gregarine-like body within the red corpuscles, which increases 

 in size until its length is 10-15 p ; it then divides into numerous 

 small or a few large gymnospores. In the first case the spores 

 may number fifty, are 3-5 p in length, occur in May or June, and 

 are exclusively within the erythrocytes ; in the latter case the 

 spores measure 5-8 \i in length, are five to fifteen in number, and 

 develop within cells in the blood-forming organs. The extra- 

 corpuscular phase, commencing within the corpuscles, ends in an 

 elongated organism possessing a vermicular movement, and free 

 in the plasma. Similar parasites are frequent in the lower verte- 

 brates, e.g. snakes. 



Order. Myxosporidia 



In this group the trophozoite is amoeboid, and the species are 

 almost exclusively parasites of fish, in the young stage being intra- 

 cellular (" fish psorosperms "). 



Order. Microsporidia 



The Microsporidia are cell parasites of invertebrates, especially 

 arthropods, and the trophozoite is more or less amoeboid. 



1 See Nultall and Grab am -Smith, Journ. of Hygiene, vols, iv to viji, 

 1904-8. 



