AMEB^E. 705 



creations. There is no progressive increase of development from the lowest 

 plant to the highest animal. The animal begins by himself, as it were, as 

 the plant, and both grow up in different directions. The protozoa exist 

 upon organic substances, while plants absorb inorganic substances and 

 assimilate them. -* 



The Gregarinida are very tiny cells, and though microscopically minute, ' 

 they sometimes develop into worm-like or elongated oval bodies. They 

 inhabit the intestines of Crustacea, worms, and cockroaches, as well as of : 

 higher animals. They are capable of certain motion, but are not furnished 

 even with the " false feet " {pseudo podia} of the rhizopoda, the next animal 

 in these very low scales of creation. 



Of the Rhizopoda the AMEB^S are very interesting, and we find them 

 in our veins as well as in the stagnant green water of the pond. They are 

 simply sarcode or jelly, and, as the name implies, the amebae can change 

 their appearance (amoibos, changing). They possess a kind of crawling, 

 progressive motion, and under the microscope will be perceived to develop 

 a tiny bud, as it were, which is the " false foot " that assists its progress. 

 These amebae are in our blood moving about, and are always altering their 

 form, and when warm they move more quickly in the red blood corpuscles 

 or cells, but excessive heat will kill them. 



These curious creatures feed by the foot they protrude ; and by drawing 

 in the "process" as it is termed, they can collect within themselves the 

 nourishment they require. Of course they have no mouth, and if we can 

 conceive a creature of this kind which thrusts out from a jelly-bag a tiny 

 lump, and pulls it in again at any time and place it likes, we have an idea 

 of an ameba. 



The pond ameba is somewhat different from the others, inasmuch 

 as it possesses an outer and inner portion or layer which are different 

 in density. There is what is termed a contractile vesicle which "beats" 

 as a heart beats, but this is very primitive. There is really no structure 

 whatever in these rhizopoda, and, as we have seen, their shape is always 

 undergoing change. The outer and inner layers of the amebae are called 

 " the ectosarc " and " endosarc " respectively ; the latter contains the darker 

 portion the nucleus. 



The Foraminifera have already been mentioned in the chapters on 

 Geology. We find these minute creatures must have had a great deal to 

 do with the building up of rocks, as they have the power to make tiny 

 coverings for themselves, which have been built into rocks by the addition 

 of sandy particles, and consolidated by pressure. Here we have a most 

 wonderful instance of the tiniest creatures producing the greatest masses 

 of the earth. The body is merely sarcode, the shell is carbonate of lime. 

 The foraminifera produce false feet in abundance, which surround the cell 

 like fine hairs or rays. They live in the sea, and when they die the shells 

 descend upon the ocean floor, where they undergo many changes and 

 become converted into rock. The ooze of the great oceans is composed 



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