134 KANSAS CITY REVIEW OF SCIENCE. 



pushed on upward toward Man. And the eighth stage Haeckel calls the Chor- 

 domum—\ha.\. is, when in the developing embryo (human) the first faint inklings 

 of a dorsal chord begin to appear. This stage is represented in modern zoology 

 by animals called Appendicularia, which are in appearance precisely like the em- 

 bryo at this stage. 



The ninth stage is called Acrania, or headless animal, and is the primordial 

 vertebrate — the backbone, though merely rudimentary, being now distinctly indi- 

 cated. This stage is represented by the animal called lancelet or Amphioxus, 

 which Haeckel, himself, first demonstrated to be a true vertebrate and the transi- 

 tional form or connecting link between the worm class and the vertebrate class. 

 He thinks, at one period in the world's history animals of this type predominated 

 and were the highest forms yet brought forth ; but because of their having no hard 

 parts their remains are not found in the rocks. 



The tenth stage is the Monorhifia, meaning that the mouth and nostrils are 

 one — the nearest rudimentary development toward a specialized head ; and this 

 stage is now represented by the lamprey eel and the hag-fish or Myxine. The 

 eleventh stage is Amphirhina, or mouth and nostrils differentiated. This stage 

 is represented by the Selachian group of fishes, the remains of which are found 

 certainly as low down as the Upper Silurian rocks, and they are the primordial 

 type of fishes. These fishes had only a cartilaginous skeleton and not a true 

 vertebral column or backbone; but their brain and nervous system, as also the 

 heart and the organs of the senses were more highly developed than in the true 

 bony fishes even of the present time; and their embryos showed a decided ap- 

 |)roach toward the amphibians. The modern rays, sharks, and some others, be- 

 long to this class of fishes. At this stage in the zoo geological scale, according to 

 Haeckel, the line of the bony fishes branched off, while the upward line develop- 

 ed into the twelfth stage, called Dipneusta — that is, double-breathers (having gills 

 and lungs both), a type which is now represented by the animal called Lepidosi- 

 ren. Prof. Nicholson, whose "Manual of Zoology" is a standard text-book in 

 Scotland, the United States and Canada, says of this animal : "It exhibits a dis- 

 tinct transition between the fishes and the amphibia,'' (p. 399.) Andagain : "It 

 may justly be looked upon as a connecting link or transitional form between the 

 two great divisions of the fishes and the amphibians," (p. 401). 



The next or thirteenth stage is c lied Sozobranchia, which means that they 

 retain their gills through life although they cease to use them. The modern Pro- 

 teus, the Siren, and the Menobranchs represent this stage. The fourteenth is the 

 Sozura — that is, retaining the tail through life, and which type is represented now 

 by the Tritons and Salamanders. From this stage the Batrachian class branched 

 off, as represented by the gigantic extinct labyrinthodonts and the modern toads, 

 frogs and salamanders. 



Fifteenth is the Protamnion — a supposed animal in which a foetal membrane 

 first began to be developed, instead of the spawning process of the amphibian and 

 lower forms. This stage is located as probably in the Permian period of geology, 

 which was a great revolutionary or transitional epoch, a sort of interspaced 



