SPOKOZOA 749 



times divided into two. The zone (2) immediately surrounding 

 the central corpuscle is usually more or less distinctly granular. 

 and sometimes has an almost bead-like margin. The narrower 

 outer zone (3) is generally clear, transparent, and structureless. 

 but sometimes shows radiating stria?. When viewed sidewise or 

 obliquely, however, the ' cyatholiths ' are found to have a form 

 somewhat resembling that of a shirt-stud (figs. 1, 2, 7). Each con- 

 sists of a lower plate, shaped like a deep saucer or watch-glass ; of 

 a smaller upper plate, which is sometimes flat, sometimes more or 

 less concavo-convex ; of the oval, thick-walled, flattened corpuscle, 

 which connects these two plates together at their centres ; and of 

 an intermediate granular substance which more or less completely 

 fills up the interval between the two plates. The length of these 

 cyatholiths ranges from about yeViyth to w L-Qth of an inch, those of 



IT oVo f an i ncn an d under being always circular. It appears 

 from the action of dilute acids upon the coccoliths that they must 

 mainly consist of calcareous matter, as they readily dissolve, leaving 

 scarcely a trace behind. When the cyatholiths are treated with 

 very weak acetic acid, the central corpuscle rapidly loses its strongly 

 refracting character ; and there remains an extremely delicate, 

 finely granular membranous framework. When treated with iodine 

 they are stained, but not very strongly, the intermediate sub- 

 stance being the most affected. Both discoliths and cyatholiths are 

 completely destroyed by strong hot solutions of caustic potass or 

 soda. The coccospheres (fig. 3) are made up by the aggregation of 

 bodies resembling ' cyatholiths ' of the largest size in all but the 

 absence of the granular zone ; they sometimes attain a diameter of 

 T (joth of an inch. What is their relation to the coccoliths, and 

 under what conditions these bodies are formed, are questions whereon 

 no positive judgment can be at present given. 



SPOROZOA. 



The term Sporozoa was applied by Leuckart to a group of 

 protozoic animals of which the well-known Gregarinida, the Coccidi- 

 idea, the Ha?mosporidia, the Myxosporidia, and the Sarcosporidia ! are 

 the chief divisions. They are especially characterised by the peculi- 

 arities of their mode of reproduction, in which a period of encystation 

 (which may or may not be preceded by conjugation) is succeeded by 

 the breaking up of the contained protoplasm into a large number of 

 small ' spores,' the products of which become intracellular parasites. 



The Gregarinida lead a parasitic life, and may often be met with 

 in the intestinal canal or other cavities of earthworm, insects, &c., 

 and sometimes in that of higher animals. An individual Greyarina 

 essentially consists of a large single cell, usually more or less ovate 

 in form, and sometimes attaining the extraordinary length of two- 

 thirds of an inch.' 2 A sort of beak or proboscis frequently projects 

 from one extremity ; and in some instances this is furnished with a 



1 Consult the memoir by Dr. K. Blanchard in Sail. Soc. ZooL France, x. p. '244. 



- See Prof. Ed. Van Beneden on Oregarina gigantea (found in the intestinal 

 canal of the lobster) in Quart. Journ. Microsc. Sci. n.s. vol. x. 1870, p. 51, and vol. 

 xi. p. 242. 



