44 PROTOZOA [CH. 



Sporozoa, suggested by the frequently recurring formation of spores, 

 which is a marked feature in the life-history, is inappropriate, as we 

 have seen reason to believe that something analogous occurs in all 

 Protozoa; but it is characteristic of Sporozoa that the contents of 

 each spore break up into a number of amoeboid young. All the 

 Sporozoa are parasitic; that is to say all live at the expense of 

 some other animal which is termed the host. All as a matter of 

 fact pass the first period of their existence embedded in the protoplasm 

 of some animal. Some the Cocci dea remain throughout life 

 in this position, but others when fully grown become at any rate 

 partly free, adhering to their hosts only by one end. Only fluid 

 nourishment is absorbed and consequently there is neither mouth 

 nor anus. The Sporozoa are thus contrasted with the Haemato- 

 flagellata which appear to pass all stages of their existence in the 

 fluids of their host. There is usually one nucleus, although the 

 body may be divided into two or even three portions by partitions 

 running across the protoplasm placed one behind the other. 

 Reproduction takes place by fission and by the production of naked 

 germs which conjugate called gametes. The resulting zygote secretes 

 a cyst wall and forms the spore. The contents of this spore break 

 up into several so-called "falciform embryos" which are really 

 amoeboid young. 



Among the better known Sporozoa are Monocystis found in the 

 vesicula seminalis of the Earthworm, with a long worm-like undivided 

 body, Clepsidrina blattarum found in the intestine of the Cockroach 

 and C. longa in the intestine of the larval grub of the Daddy-long- 

 legs, which lives in damp soil. This last form is quite free when 

 adult and is distinctly divided into two portions. 



In recent years it has been discovered that many of the Sporozoa, 

 like the Haematoflagellata, cause disease, and a great amount of 

 study has been devoted to this group. Leaving out of consideration 

 the little known Neosporidia in which fission and the formation of 

 spores go on at the same time, the more normal Sporozoa are divided 

 into three groups, viz. Gregarinidea, Coccidea and Haemosporidia, 

 To the first named belong the two forms just mentioned. In this 

 family two fully adult individuals termed trophozoites approach 

 one another and become surrounded by a common cyst wall, termed 

 the sporangium. Within this both break up into gametes, and the 

 naked oval gametes conjugate in pairs. The zygotes then surround 

 themselves with boat-shaped flinty cases and become the spores, or 

 " pseudonavicellae," the contents of each of which breaks up into 



