1 90 POPULAR SCIENCE MONTHLY. 



Sporozoa is that, notwithstanding the many kinds and the wide distri- 

 bution in all sorts of hosts, the life history of the parasites invariably 

 conforms to the same type, a fact which has recently been used to 

 good advantage in working out the development of the malaria or- 

 ganism. 



Like all the unicellular animals, or Protozoa, the Sporozoa are 

 minute bits of protoplasm provided with a membrane and a specialized 

 spherical portion of the inner protoplasm called the nucleus. Unlike 

 the other Protozoa, they are entirely devoid of motile organs and are, 

 in consequence, quiescent. In classifying them, advantage has been 

 taken of the different modes in which they form spores, or germs, by 

 which they are reproduced. In some, known as the Telosporidia, all 

 the protopla-sm of the parasite is used to form the spores, and the parent 

 cell dies or disappears with each sporulation, which thus represents 

 the end of the individual parasite. The individuals of the second 

 group, known as the Neosporidia, form spores, without using all the pro- 

 toplasm, and continue to live after each sporulation. This group 

 comprises the less-known forms of Sporozoa, and is of considerable 

 economic importance as the cause of epidemics among silkworms, 

 brook trout and other fish, etc. 



The Telosporidia are further divided according to the mode of 

 life. Some of them, known as the Gregarinida, live in cavities of the 

 body of many forms of invertebrates, but rarely in vertebrates; others, 

 the Coccidia, live in epithelial cells lining the cavities of both inver- 

 tebrate and vertebrate hosts. It may be remarked, parenthetically, 

 that the cause of cancerous growths in man is claimed by many to be 

 organisms belonging to this group of Sporozoa. The question remains 

 in considerable doubt, however, and, despite the great mass of litera- 

 ture, no positive results have appeared. The last group finally of the 

 Telosporidia is the Hcemosporidia, comprising parasites which, like the 

 malaria-organism — Plasmodium malarice — live in blood corpuscles of 

 vertebrates. 



All these different types of Telosporidia begin life as minute germs 

 called sporozoites, which make their way into the new host through the 

 intestine, being taken in with the food. The life history, after this 

 ingestion, follows slightly modified paths in the different types, and, 

 for purposes of comparison, I will describe these processes in the greg- 

 arine, the coccidium and in the hsemosporc Plasmodium malarias, thus 

 representing each of the subdivisions of the Telosporidia. 



The sea-squirt, or Tunicate, Ciona intestinalis, is the host of a 

 gregarine Monocystis ascidiw, which is so widely distributed that it is 

 almost impossible to find a Ciona without them. The complet e life his- 

 tory of the parasite has been fully worked out by Prof. M. Siedlecki, 



