RHIZOPODA. 



15 



stance, sometimes colorless and transparent, sometimes distinctly colored yellowish or 

 brown, while still others are covered with grains of sand. 

 A very frequently occurring 



form is Pseudodifflugia. In this 

 the shell is chitinous, with sand- 

 grains in some wise incorporated 

 with it. It resembles Difflugia, 

 Fig. 3, in every respect except as 

 regards the character of the pseudo- 

 podia. In some of the genera the 

 shells are beautifully marked, and 

 the neck is often curved so that the 

 body lies on the side as the animal 

 crawls along. 



SXJB-ORDEE II. — 

 FEEA. 



FOEAMINI- 



FlG. 11. — Gr(ymia oviformis, enlarged 600 times. 



The Poraminifera embraces an 

 almost innumerable variety of ma- 

 rine Rbizopods. The reticulate, 

 anastomosing nature of the pseudo- 

 podia is most strikingly manifest 

 in all the Foraminifera, but the ex- 

 amination of the internal sarcode is 

 very difficult, owing to the thick- 

 ness and opacity of the shells. For 

 this reason it was long supposed 

 that the Foraminifera were desti- 

 tute of a nucleus, but recent inves- 

 tigations by Hertwig and Lesser, 

 Carpenter and others, have revealed nuclei in several forms, and they are doubtless 

 present in all of them. It is said that dahlia violet will stain the nuclei while the 

 animal lives, and if this is true in all cases, it will prove a valuable reagent in further in- 

 vestigations of those organisms. 



The Foraminifera are the only Rbizopods that have shells of many chambers, and 

 of complex structure. The different forms of the shells can best be understood by 

 observing how they are derived from a single chamber by the budding oE of successive 

 portions of the sarcode-body, each of which then secretes a shelly covering. If the 

 budding always takes place in the same direction, an elongated form composed of 

 several chambers in a straight line is produced, as in Lagena. If the tendency of 

 growth is to produce a spiral, it results in the beautiful Cornuspira, which greatly 

 resembles the mollusc Planorbis, or, if the budding takes place in still another way, 

 the more complex forms of Miliola are produced, which are only spirals greatly 

 elongated in one direction. Instead of forming successive single chambers at the ends 

 of old ones ; the growing spiral may spread out wide and ilat, thus forming the beauti- 



