MAN'S ZOOGENETIC LINEAGE. 133 



happens to arise. It is for this reason also called pseudopoda — that is, false-footed, 

 or not-to-be-depended-on footed. 



There are many different species of amoebae, and here the differentiation or 

 divergence of specializing lines of animal structure already commences. And 

 the next advance stage of animal life is the Protozoa, of which Professor Tenney, 

 " Elements of Zoology," says: " The protozoans are probably more numerous 

 than all other animals of the globe. *>!<>{= Rocky strata, hundreds 

 of feet in thickness are wholly made up of their remains." 



From the protozoan stage branched out many divergent forms, but the main 

 trunk of the tree of life, according to Haeckel, kept on steadily toward Man. 

 The third stage he calls Syfiamoeba, or synthesized or compound amoeba. The 

 fourth stage is Flanceada, a form of animal hfe corresponding to what is familiar to 

 well-educated physicians as the blastosphere stage of embryonic development — a 

 hollow sphere with walls composed of a single layer of cells. The fifth stage is 

 Gasirceada, or the stomach-animal — a speciaHzed digestive sac, with one opening 

 to serve at once as mouth and ventrum. Its walls are composed of two cellular 

 layers instead of one ; and it is laid down as an established law of embryology 

 that in all animal embryos at this stage, it is from the outer layer or exoderm that 

 are developed the outer skin, hair, nails, feathers, scales, horns, hoofs, and all 

 the organs of locomotion and external sensation ; but from the inner layer, or 

 entoderm, are developed the inner lining of the entire cavity of the body, also 

 the glands and organs of nutrition, and the lungs, liver, heart, etc. Haeckel 

 holds that as low down in the geological scale as the Laurentian period (see Geo- 

 logical Chart as above referred to) this form of animal must have existed quite 

 extensively, as a free inhabitant of the yet simmering seas ; but it had no hard 

 parts of bone or shell or strong incasement, and therefore left no relic of its form 

 or locality. The nearest living representatives of this hypothetical Gastrseada are 

 the larval forms of what are called in zoology ascidians or tunicata — a class of 

 animals composed simply of a tunic or sac. They are sometimes called salps, or 

 salpid^, and you will find them described and figured in any recent good text 

 book of zoology. 



The next or sixth stage is called Archelminthes, or the primordial worm. The 

 sac has become annulated or ring hke, and has developed an intermediate layer 

 of cells between the outer and inner layers of the gastrula stage. This vermi- 

 form stage is found in all higher animal embryos, and is represented by the 

 zoological order of worms called Turbellaria. The seventh stage is a very 

 slight modification of the last, and is called Scolecida, which is a general term 

 for a large class of worms, some of them, like the Turbellaria themselves, being 

 composed .of only one joint or ring, and others of more; and here the pig- 

 ment spots or rudimentary eyes are first detected. From the Scolecida stage 

 of paleozoic life, as Haeckel thinks, branched off the line that developed the 

 articulata — that is, all jointed animals, like crabs, lobsters, spiders, scorpions, 

 bugs, ants, and insects of every sort ; and also the line that developed the 

 whole vast realm of molluscan life. But the main trunk of the tree of life 



