EvoLrTiON OF Animals 379 



cilia or flagella, have a definite outline, and often a highly 

 specialized body structure. Here it may be remarked how- 

 ever that we would not regard the former or pseudopodial 

 group as necessarily the older or more primitive. 



The 17 genera of Lobosa include 14 that are fresh-water, 

 1 that is adaptable to fresh or salt water, and 2 that are marine. 

 In structure also they show graded transitions from types 

 that closely resemble the higher Proteomyxa to others that 

 become testiferous and exhibit easy passage to the fresh-water 

 Foraminifera. 



The genera of the Mycetozoa are wholly land types, and 

 are 48 in number. The species according to Lister amount to 

 about 280. The Heliozoa include about 30 genera of which 15 

 are fresh- water; 5 contain species that are mainly so, but are 

 in part marine; 8-10 genera are wholly marine. As some genera 

 of the Lobosa show graded passage to the Foraminifera, so 

 do some members of the present group show suggestive trans- 

 itions to the Radiolaria. 



The Foraminifera can best be treated numerically, as they 

 seem to have evolved morphologically, namely, as composed 

 of two groups, a more primitive one that includes simple forms 

 \\4th mostly chitinous or adventitiously derived tests, like 

 Diplophrys, Lieberkvhnia^ and Pseudodiffugia; and a more 

 advanced group ^ith simple or more often complex test in- 

 crusted with carbonate of lime, as in most of the marine species. 

 The former group includes 12 genera that are fresh- water, 2 

 that are fresh- or brackish-water, 2 that are mainly fresh- 

 water but in part marine, and 5 that are marine. But migra- 

 tion of some of the ancient and primitive representatives from 

 fresh water into brackish and eventually salt water, has here 

 resulted — we would consider, as in nearly every animal genus 

 that so migrates — in production of a great wealth of foramin- 

 iferous genera and even more of species, that are as complex 

 and beautiful in their shell structure as they are iti their nuclear 

 structure and mode of conjugation. 



The Radiolaria run fairly parallel to the last group in numer- 

 ical and morphological value. But as often restricted and 

 defined in text-books, the group includes a great and diverse 

 assemblage of genera that are purely marine, are extremely 

 rich in species, and are highly pleiomor]3hic. As explained 

 later (p. 382) it would seem a preferable treatment were such 

 genera as Acanthocystis, Pinacocystisy LitJiocoUa, etc., which 

 are fresh-water, removed from the Heliozoa, also Euglypha, 

 Trinema, various of the Astrorhizidea and Lituolidea, removed 

 from the simpler Foraminifera, and placed as generalized 



