312 THE DOCTRINE OF DESCENT. 



rerum ex omni specie viventium unicum sexus par fuisse creatunij 

 suadet ratio." 



15 Ib. Non multum a veritate me aberratum confido, si dixerim, 

 omnem continentem terram fuisse in infantia mundi aquis sub- 

 mersam et yasto oceano obtectam, praeter unicam in immenso 

 hoc pelago insulam, in qua commode habitaverint animalia omnia 

 et vegetabilia Isete germinaverint." 



16 Tot numeramus species, quot ab initio creavit infinitum ens." 



17 Geoffroy St. Hilaire wrote to Cuvier : " Venez jouer parmi 

 nous le role de Linnd, d'un autre legislateur de 1'histoire naturelle." 



18 Ossements fossiles. 



19 L. Agassiz, An Essay on Classification, 1859. P. 253: 



" As representatives of Species, individual animals bear the 

 closest relations to one another ; they exhibit definite relations also 

 to the surrounding element, and their existence is limited within a 

 definite period. 



" As representatives of Genera these same individuals have a 

 definite and specific ultimate structure, identical with that of the 

 representatives of other species," etc. See also P. 261 : 



" Branches or types are characterized by the plan of their struc- 

 ture; 



" Classes, by the manner in which that plan is executed, as far 

 as ways and means are concerned ; 



" Orders, by the degrees of complication of that structure ; 



" Families, by their form, as far as determined by structure ; 



" Genera, by rhe details of the execution in special parts ; and, 



" Species, by the relations of individuals to one another, and to 

 the world in which they live, as well as by the proportions of their 

 parts, their ornamentation," etc. 



20 Haeckel, Generelle Morphologic der Organismen (Berlin, 1866). 

 II. 323, &c. 



*' L'espece est "la reunion des individus descendant 1'un de 

 1'autre et des parents communs, et de ceux qui leur ressemblent 

 autant qu'ils se ressemblent entr'eux." Cuvier, Le Regne Animal. 



"* O. Schmidt, Die Spongien der Kiiste von Algier, 1868, and 

 Versuch einer Spongienfauna des atlantischen Gebietes, 1870. 



a3 Haeckel, Die Kalkschwamme. Eine Monographie in Zwei 

 Banden, Text und einem Atlas mit 60 Tafeln Abbildungen (Berlin, 

 1872). 



