180 ESSAY ON CLASSIFICATION. 



Among the Echinoderms,we find in the order of Crinoids 

 the pedimculated types standing lowest, 1 Comatulee highest, 

 and it is well known that the young Comatula is a pedun- 

 culated Crinoicl, which only becomes free in later life. 2 

 J. Mliller has shown, that, among the Echinoids, even the 

 highest representatives, the Spatangoids, differ but slightly 

 in early youth from the Echinoids, and no zoologist can 

 doubt that these are inferior to the former. Among the 



o 



Crustacea, Dana 3 has insisted particularly upon the serial 

 gradation which may be traced between the different types 

 of Decapods, their order being natural from the highest 

 Brachyura, through the Anomoura, the Macroura, the 

 Tetradecapods, etc., to the Entomostraca. The Macrouran 

 character of the embryo of our Crabs has been fully illus- 

 trated by Rathke, 4 in his beautiful investigations upon the 

 embryology of the Crustacea. I have further shown that the 

 young of the Macroura represent Entomostracan forms, 

 some of them having even been described as represen- 

 tatives of that order. 5 The correspondence between the 

 gradation of Insects and their embryonic growth I have 

 illustrated fully in a special paper. 6 Similar comparisons 

 have been made in the class of Fishes ; 7 in that of Eeptiles 

 we find the most striking examples of tin's kind among 

 Batrachians 8 (see above, Sect. XII.) ; in the Birds, 9 the uni- 

 formly webbed foot of all the young, exhibits another cor- 

 respondence between the young of higher orders and the 

 permanent character of the lower ones. In the order of 



1 MiiLLER (J.), TJeber Pentacrinus 4 RATHKE, q. a., p. 119. 

 Caput Medusae ; Berlin, 1833, 4to., 5 Twelve Lectures, etc., p. 67. 

 Ak. d. Wiss. e Classification of Insects, q. a. 



2 FORBES (En ), History of British 7 Poissons fossiles, q. a. 

 Starfishes; London, 1851, 1 vol. 8vo., 8 Twelve Lectures, etc., p. 8. 



P- 10 - 9 AGASSIZ (L.), Lake Superior, etc., 



3 DANA, q. a., p. 45. BURMEISTER, p. 194. 

 Cirripeds, q. a., p. 119. 



