Class 1. Gymnomyxa. Order 1. Rhizopoda. 



89 



(Globigerina) . Similar beds of Rhizopod shells have also been 

 deposited in earlier times, and these, though in a more or less 

 fragmentary condition, form a consider- 

 able part of important geological strata 

 (chalk). 



A m ce b 8B with lobate pseudopodia and without 

 shells (c/., p. 3-5) occur both in salt and fi-esh 

 water. Several genei^a. with simple uniloculaj- 

 chitinous shells (sometimes covered with foreign 

 bodies) ai-e found in fresh water (Fig. 47 A, B). 

 One of the numerous marine sheU-beaiing f onns, 

 which ai-e often exti-emely fi-agile, is drawn iu 

 Fig. i~ C. Among the veiy numerous fossil forms 

 may be mentioned the genus NuniniulHes (Fig. 48), 

 distinguished by its size, which is, for a Protozoon, 

 enormous. 



ii^. 48. Suinrnttlites d-uitans, 

 natural size; the figure or 

 the left represents an example 

 which has been longitudinally 

 dissected ; that on the right, 

 a transverse section. — After 

 .Irchiac and Haime. 



Order 2. Eadiolaria. 



The Eadiolaria differ from the RhizojDoda, in possessing a 

 central capsule, a porous membrane enclosing the greater 

 portion of their protoplasm. Outside the central capsule there 

 is a thin protoplasmic sheath, and outside this again, a thinner 

 or thicker sheath of gelatinous material. The body is typically 



Pig. 49 A. Diagrammatic figure of a Eadiolarian from which the skeleton has 

 been r-moved. c central capsnle, g jelly veil, k nnclens, p psendopodia. — Orig. 

 Fig. 49 B. Skeleton ofaEadiolaria n. — After Haeckel. 



spherical; but the deviations from this type are numerous. In 

 addition to the capsule, there is usually a well-developed 

 skeleton, which generally consists of silica (occasionally of an 

 organic substance); it varies considerably in the different forms. In 

 some it consists of a number of isolated spines which radiate from the 



