16 SOME MINUTE ANIMAL PARASITES 



ment, and habitat, but the essential feature of spore 

 formation appears in all. Again, in some members 

 of the Sporozoa there is a high differentiation of sex 

 shown. It is doubtful if proof of true sexual charac- 

 ters has been shown in the classes of Protozoa pre- 

 viously mentioned, and even in the remaining group 

 of Protozoa the Ciliates the sexual differentiation 

 in the form of the organism is by no means so com- 

 plete as in the Sporozoa. At the same time, the 

 whole life-cycle of certain of the Sporozoa is very 

 imperfectly known, and in some cases asexual repro- 

 duction may be the most familiar feature in the 

 organism's history, while the sex forms, if any, are 

 unknown. 



The Sporozoa are very varied. Among them are 

 found the delicate malarial parasites ; the more 

 massive parasites of the blood-scavengers, the leuco- 

 cytes ; the wormlike parasites of the meal-worms 

 (dear to the angler), and many other lowly animals 

 known as Gregarines ; the parasites of the alimentary 

 canal of man, other mammals, and birds, known as 

 the Coccidia, a group of enormous economic im- 

 portance ; the 'parasites responsible for the pebrine 

 disease among silkworms and a similar one among 

 bees, the parasites belonging to the genus Nosema; 

 the organism Rhinosporidium that produces nasal and 

 aural polypi in man ; and many others. The economic 

 importance of the group as a whole is immense, and 

 demands much careful research and study. 



Finally, the last great section of the Protozoa is 

 the Infusoria, and it includes all the Ciliata. These 

 organisms have the act of movement carried out by 



