50 TRANSACTIONS OF THE [NOV. 16,. 



Alfred "Wallace, at the same period, visiting the Malay Archi- 

 pelago, curiously arrived at similar conclusions to those enun- 

 ciated in that work. H. W. Bates, during his observations on 

 the Amazon, also came to like conclusions. Fritz Aluller, 

 Haeckel, and Weissman are also identified with the same line of 

 thought. 



In this country, Hyatt, Cope, Dall. Ryder, and Packard are 

 supporters of the doctrine. The well-known names of Huxley, 

 Spencer, and Asa Gray are prominent expounders. In Germany, 

 Semper is its prominent representative. 



The year 1839 commenced a period notable for the appre- 

 ciation, by Schwann, of the aninud cell. Valentine, during the 

 same year, adopted terms for the expression of the new views. 

 The cellular theory was then given to tlie scientific world. In 

 1665, Robert Hooke distinguished the cells of i)lants, and termed 

 them cells and ])ores. The terms nucleus and nucleolus were 

 ap]died by Sciiwann. 



Dujardin and W. Schultze had determined that protoplasm, a 

 word invented by Purkinje, is the basis of life, and the cell the 

 unit of organization. 



Carney, in " La Biologie CeUuhn're," published the his- 

 tory and facts relating to the doctrine of i)rotoi)lasm. and its 

 identity in both animal and vegetable tissues or cells. The term 

 "sarcode" is used by Dujardin at this i)eriod, but has since 

 become well-nigh obsolete. 



Briike, Kiihne and Schultze were now, 1861, active in this line 

 of study. TMie .treatises on embryology by Agassiz, Haeckel, 

 Von Baer, and Packard, and latterly by J3alfour, in "Compara- 

 tive Embryology,^' embody the most advanced views in this line 

 of study. 



The discovery of spermatozoa, by Leeuwenhoeck, in 1677, and 

 the mammalian egg, by Dograaf, were imi)ortant events in the 

 progress of embryology. 



Eemak, in 1850, exhibited the existence of three germinal 

 layers. Huxley, in 1859, pointed out the homology of these 

 with the tissues of the coelentcrates. Hertwig, Lang, and Sedg- 

 wick followed in a still further elaboration of this subject. 



Among others identified with theeluciilation of the structure 

 of the invertebrates may be mentioned Hyatt, whose labors vvith 

 the sjionges and the aminonites are notable for great value, and 

 Meek, Leidy, Marsh, and Cope, In Europe, the names of Bois- 

 duval, Bouciie, Wyville Thompson, and his associates of the 

 ClidUenger, Von Suhm, Moseley, in 1872-76, are associ ited 

 with work destined to enduring fame. So, also, is the Poi'cnpine 

 expedition, whose naturalists were the eminent Carpenter antl 

 Jeffreys. 



