42 GENESIS OF MAN. 



fish-form is not that of a true Tclcost, or ordinary bony fish, but of 

 a Selachian. Indeed, the higher fish-form is never attained, but the 

 embryo skims along at the bases of the great ichthyic and amphi- 

 bian branches, without becoming at any time a true fish or a true 

 Batrachian. This is a very significant fact, and one which, while it 

 is easily accounted for by the general theory of descent, forms at 

 the same time a powerful ontogenetic argument for the truth of 

 that theory. For the typical representatives of any great group 

 exhibit only the extremities of greatly differentiated branches remote 

 from the parent stem, and it is not to be expected that in the 

 corresponding embryonic forms of animals higher up the stem we 

 should see anything but copies of those forms which existed prior 

 to, or at the commencement of, ramification, and which are conse- 

 quently within the common line of descent of both. 



Some will, perhaps, regret that their ancestors should have been 

 worms, while they cannot count in their pedigree either the bee or 

 the ant ; others may not feel flattered to be informed of their close 

 relationship with the frog and the toad; but few, I think, will be 

 sorry to learn that their forefathers were not reptiles, though this 

 fact precludes the more pleasant thought of claiming relationship 

 with the birds ; for birds, with all their grace, beauty, and inno- 

 cence, are neither more nor less than transformed reptiles. 



The human embryo passes along the base of the Batrachian 

 branch and through the Sozura (thus saving its tail) and so keeps 

 quite aloof from the whole race of lizards, snakes, turtles, etc., and 

 a fortiori, of birds. The unborn man is first a Selachian, then a 

 Lepidosiren, then a Siren, and finally a Triton. His first limbs are 

 fins, his first respiratory organs are gills, and his lungs are at first 

 fish-bladders. 



The tenth and last stage of ontogenetic progress is denominated 

 by Haeckel the Amnion-stage . This stage embraces not only that 

 of all true mammalian forms, but also takes in the two inter- 

 esting antecedent groups, the Monotremata and the Marsupialia. 

 Haeckel establishes a hypothetical Protamnion, which he locates 

 in the Permian period, and which he claims to have been the 

 original progenitor of all the Amniota, or amnion-bearing animals. 

 The distinguishing characteristic of this embryonic form, as the 

 name implies, is the beginning of the development of the impor- 

 tant organ known as the amnion, which is simply a large extension 

 of the yolk-sack, and is filled with a nourishing fluid. This fluid 



