haeckel's ANTHROPOGENIE. 24:1 



Phylogenesis is ctiefly an inductive science, built up on facts 

 derived from ontogenesis, palaeontology, comparative anatomy, dystele- 

 ology, &c. ; but it must also be regarded as a comjDrehensive deductive 

 law, inasmucb as it alone is capable of reconciling all the appearances 

 ■with which we are acquainted. To apply it we must form special 

 deductive hypotheses. Such, however, cannot be complete as long as 

 our soiirces of information are incomjjlete, and the construction of a 

 genealogical tree will vary with the amount of material which is at 

 our command to work with. However, somewhere about twenty-two 

 forms can be indicated as ancestral, eight of them invertebrate, four- 

 teen vertebrate, eleven archozoic, three palaeozoic, three mesozoic, four 

 cainozoic. In considering these, it will be convenient to refer at the 

 same time to the nearest living representatives, and to the stages of 

 ontogenesis to which they correspond. 



The Monera are ■ the simplest organisms with which we are 

 acquainted, being formed of simple plasma, cytodes indeed, and not 

 cells. There are forms which live in colonies (protomyxa), but the 

 simple forms like protamceba must be regarded as the starting point 

 for all organisms, vegetable or aniinal. One of the most interesting 

 of the monera is bathybius, its existence necessitating spontaneous 

 generation, and showing us how the transition from an organic car- 

 bonaceous substance to liAdng matter just as little requu-es super- 

 natural interference as the slow evolution of higher from lower 

 forms. This ancestral foi'm is repeated in ontogenesis by the "mone- 

 rula " stage, that which results from the disappearance of the nucleus. 



The amoeba is a simple cell, diJSering from the protamceba in 

 the possession of a nucleus, and evidently developed from such a 

 moneron. The similaritv between the amoeba and the earor-cell cannot 

 be too strongly insisted on, although it is sometimes masked by the 

 development of a limiting vitelline membrane. 



The synamoebium was formed from the amoeba, and consisted of 

 a colony of amoeboid organisms developed by repeated fission, but 

 remaining in connection. The nearest living representatives are 

 cystophrys and labyrinthula ; and the " morula " stage recapitiilates 

 this in the onogenetic process. 



The plansea was a hollow, globular animal, the wall of the body 



formed of a single layer of ciliated cells, represented in ontogenesis 



by the blastosphere or planula, and at the present day by magosphsera 



planula — a peculiar organism discovered by Haeckel on the coast of 



5 



