Chap. X. CLASSIFICATION. 101 



whole extent.'' It is certain, however, that views essen- 

 tially similar are still to be met with everywhere in 

 discussions on classification, and that even within the 

 last few years, the very sparingly successful attempts 

 to employ develoj)mental history as the foundation 

 of classification have been repeated. 



But how do these propositions agree with our obser- 

 vations on the developmental history of the Crustacea ? 

 That these observations relate for the most part to 

 their "free metamorphosis" after their quitting the 

 egg, cannot prejudice their application to the pro^Dosi- 

 tions enunciated especially with regard to " embryonal 

 development " in the egg ; for Agassiz himself points 

 out (§ 391) that both kinds of change are of the same 

 nature and of equal importance and that no " radical 

 distinction " is produced by the circumstance that the 

 former take place before and the latter after birth. 



" The ovarian eggs of all animals are identical, small 

 cells with vitellus, germinal vesicle and germinal 

 spot." Yes, somewhat as all Insects are identical, 

 small animals with head, thorax, and abdomen ; that is 

 to say if, only noticing what is common to them, we 

 leave out of consideration the difference of their de- 

 velopment, the presence or absence and the multifa- 



^ Agassiz' own views have lately become essentially different, so far 

 as can be made out from Eud. Wagner's notice of his ' Essay on Classi- 

 fication.' Agassiz himself does not attempt any criticism of the above 

 cited older views, which, however, are still widely diffused. With his 

 recent conception I am unfortunately acquainted only from K. Wagner's 

 somewhat confused report, and have therefore thought it better not to 

 attempt any critical remarks upon it. 



