INTR OD UC TION 2 9 



ancestors similar to themselves. They found that the spores which 

 burst from the encysted forms were at first far beyond the limits of 

 vision even with the high powers of the microscope at their command, 

 but remained together in the form of a "glairy" mass in which 

 minute specks soon appeared, and these specks were watched until 

 they had become full-grown monads similar to the original form. 



In later years the theory of spontaneous generation has been limited 

 almost exclusively to the bacteria, but even here it has been energeti- 

 cally and successfully opposed by Pasteur, Tyndall, Milne-Edwards, 

 Claude-Bernard, Quatrefages, and others, against a constantly de- 

 creasing number of advocates. No one is in a position to assert, 

 however, that it does not take place in some organisms, although such 

 a view is highly improbable ; nor can it be maintained that it never 

 has taken place in the past. Many theories of "archigony " (Haeckel), 

 or the first origin of life by spontaneous generation, have been held 

 by modern naturalists ; but all such theories are of a purely inferential 

 character and lack substantial foundation. Without attempting to 

 discuss these 1 it may be pointed out that the eminent botanist Nageli 

 has advocated an hypothesis which suggests that of Buffon. Assum- 

 ing that protoplasm consists of minute structural units or " micellae," 

 he suggests that such micellae were first formed from not-living 

 matter and secondarily united into organisms. Nageli does not 

 hesitate to say that the evolution of the simplest protozob'n from 

 inorganic compounds involved a far greater step than from the first 

 organism to man, and in accordance with this idea Haeckel places the 

 beginning of life in the oldest known geologic age and in the oldest 

 period of that age, the Laurentian. This, again, is entirely specula- 

 tive ; for if we except the questionable form Eozoon, the rocks of the 

 Laurentian contain no recognizable records of past life. 2 



The rocks of the period after the Laurentian, however, the Cam- 

 brian, possess a great number of well-marked types, families, and 

 genera, thus indicating, even at this time, a considerable antiquity. 

 Haeckel and Nageli argue with Huxley, and the argument is of great 



1 For a discussion .of this topic the reader is referred to the essays of Huxley, Tyndall, and 

 Haeckel, and to Verworn's Allgemeine Physiologie, pp. 298-319. Lee's translation, pp. 

 297-319. 



2 The supposed genus Eozoon (" dawn of life ") was discovered by Logan, of the Geologic 

 Survey of Canada in 1865, and the name was given by Dawson in the same year. 

 There has been a lengthy dispute, however, in regard to this supposed fossil, some asserting 

 that it is the earliest known foraminiferon, others that it is entirely inorganic. The former 

 opinion was held by Carpenter ('65, '66, etc.) and Dawson ('65, '75, etc.), the latter by the 

 majority of geologists and petrologists, beginning with King and Rowney ('66) and followed 

 by Mobius and others. Biitschli, while admitting that Dawson and Carpenter had a certain 

 amount of evidence, inclines to the opposite view, while petrologists maintain that the same 

 structure as that of Eozoon has been frequently observed in minerals forming parts of rocks 

 of undoubted igneous origin. 



