RHIZOPODA. 



15 



stance, sometimes coloi-less aud 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 cliitinous, with sand- 

 grains in some wise incorporated 

 with it. It resembles JJifflugia^ 

 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 alons^. 





1 oviformis, enlarged COO times. 



Sub-order II. — • Foraruni- 



FERA. 



The Foraminifera embraces an 

 almost innumerable variety of ma- 

 rine Rhizopods. The reticulate, 

 anastomosing nature of the pseudo- 

 podia is most strikingly manifest 

 in all the Foraminifera, but the ex- 

 amination of the intern.al sarcode is 

 very difficult, owing to the thick- 

 ness and opacity of the shells. For 

 tliis reason it was long supposed 

 that the Foraminifera were desti- 

 tute of a nucleus, but recent inves- 

 tigations by Hertwig and Lesser, 

 Cai-penter 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, aud 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 Rhizopods that have shells of many chambers, and 

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

 observing how they are derived from a single chamber by the budding off 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 tlie tendency of 

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

 resembles the mollusc Plcmofbis, or. If the budding takes place in still another way, 

 the more complex forms of Miliofa 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 flat, thus forming the beauti- 



