5o8 THE HISTORY OF BIOLOGY 



elements in the government service was opposed with all their power, and 

 many of the radical party lived for the rest of their days as independent 

 writers. Haeckel himself, however, was protected by the liberal-minded 

 Weimar Government from all unpleasant consequences and was thus en- 

 abled, though a professor, to take a leading part in the struggle. It goes 

 without saying that the natural-scientific contents of this doctrine were in- 

 fluenced by the political and social views of the antagonists, but, on the 

 other hand, this circumstance contributed towards making Darwinism popu- 

 ular and creating a widespread interest in its problems and arguments. Before 

 proceeding to describe the part Haeckel played in this struggle, however, 

 we must take a glance at the subject of research that he made his own and 

 determine how far his general scientific conclusions were based thereon. 



His work on Kadiolaria 

 Haeckel began as a microscopist; when he was at Wiirzburg his father gave 

 him a microscope and he could not find words to express his delight at all 

 that he saw in it. In fact, both the papers he wrote for his degree were on 

 microscopical subjects — his dissertation on the tissues of the river cray- 

 fish, and an essay on the pathological changes of the venous system; two 

 school essays, the former worked out under the guidance of J. Miiller, the 

 latter under that of Virchow and noteworthy as being Haeckel's only spe- 

 cialized investigation in the sphere of the vertebrates — both papers credit- 

 able in their form and contents, but not very original. His appearance as an 

 independent investigator is marked by his monumental work on the Radio- 

 laria, which is without doubt his best. It is dedicated to the memory of 

 J. Miiller and is written in his spirit; he was, in fact, his foremost predecessor 

 in that field. It contains about one hundred and fifty new and carefully de- 

 scribed and illustrated species, as well as abundant material derived from 

 observations of their structure and mode of life. It makes what were at the 

 time valuable contributions to the problem of the biology of single-celled 

 animals, and moreover, the identity established by Max Schultze of the 

 protoplasm in the higher animals and the sarcode, which had already been 

 described by Dujardin, is hereby confirmed with fresh proofs. In connexion 

 therewith several cytological observations are quoted that are of consider- 

 able general interest — on the phenomena of currents and the manifestations 

 of assimilation in pseudopods and protoplasm, and also on the power of 

 cells to absorb solid bodies. Haeckel has observed how the blood corpuscles 

 in a mollusc absorb indigo-particles injected into the blood, but he did not 

 follow up this important fact any further, it being left to MetschnikofF a 

 couple of decades later to take up the subject and make it the basis of his 

 theory of phagocytes. In regard to classification, Haeckel tries to found 

 a natural system based on affinity; it is in connexion with this that he an- 

 nounces for the first time, though tentatively, his association with Darwin's 



