482 ZOOLOGY SINCE DARWIN. 



forms, and complete series of successive developments, with which 

 paleontology has supplied us, are all the more valuable because the 

 exactitude of its descriptions, resting in part upon petrified material, 

 and the ease with which its fundamental facts can be reverified, lend to 

 most paleontological expositions a certainty and trustworthiness that 

 must often be denied to those that relate to the morphology of recent 

 animals. 



Darwin has carefully avoided the consideration of a number of ques- 

 tions whose discussion is of no great weight for his theory of selection. 

 So it is, in fact, of no importance for the latter what our conceptions 

 may be as to the origin of the simplest forms of life upon the earth, if 

 we only establish indubitably that such did exist. So also the theory 

 of descent, as well as the theory of selection, is unaffected by the fact 

 that at the time they were first advanced there was no intelligible con- 

 ception of the material basis of heredity, nor of the causes of variation. 

 The actual existence of these processes sufficed, and served as a satis- 

 factory basis for the theory. As soon, however, as — first by German 

 naturalists and philosophers — the theory of descent was expanded to a 

 new system of biological philosophy, these important questions were 

 necessarily brought forward for discussion. 



As regards the first of these questions, the primary evolution of 

 organisms, we have not yet been able to formulate a satisfactory 

 theory. As there are no chemical elements or ''vital materials" pecu- 

 liar to living beings, and no special ''vital force" has been demon- 

 strated, there remains only the supposition that the first evolution of the 

 simplest organisms must have taken place from inorganic material by 

 the action of the forces that operate in its own domain. As, however, 

 the material basis of vital processes, protoplasm, consists of combina- 

 tions of carbon belonging to the group of albuminoid bodies, the 

 attempt was made to refer the phenomena of movement that charac- 

 terize life to the peculiar chemico-physicai peculiarities of carbon. 

 But neither this so-called carbon theory of Haeckel, nor the endeavor 

 made in recent years by O. Biitschli and others to imitate by artifi- 

 cial mixtures 1 the structure and movements of protoplasm, informs 

 us how a mixture of dead albuminoid compounds can become living 

 protoplasm. 



A conception in any way satisfactory as to the first evolution of 

 living beings must be still more difficult at this time, as not only can 

 chemistry afford us no satisfactory insight into the molecular structure 

 of protoplasm, but it appears from theoretical considerations that the 

 much-cited " simple lump of protoplasm " may have a highly complicated 



l O. Biitschli, Untersuchungen iiber mikroskopische Schiiume und das Proto- 

 plasma. Versuche und Beobachtungen zur Losung der Frage nach den physikali- 

 sehen Bedingungen der Lebenserscheinungen, Leipzig, 1892, as well as later 

 publications of tbe same author in the Verhandlungen des naturh. medicinischen 

 Vereius zu Heidelberg. 



