98 HISTORY OF CRUSTACEA. Chap. X. 



Lobster with Schizopodal feet ; Faleemon, like the Crabs, 

 as a Zoea ; and Peneus, like the Cirripedes, as a Nau- 

 pHus, — and when, still, within this same sub-order Ma- 

 crura, Palinurus, Mysis and Eujphausia again present 

 different young forms, — when new limbs sometimes 

 sprout forth as free rudiments on the ventral surface, 

 and are sometimes formed beneath the skin which 

 passes smoothly over them, and both modes of deve- 

 lopment are found in different limbs of the same animal 

 and in the same pair of limbs in different animals, — 

 when in the Podophthalma the limbs of the thorax and 

 abdomen make their appearance sometimes simultane- 

 ously, or sometimes the former and sometimes the 

 latter first, and when further in each of the two groups 

 the pairs sometimes all appear together, and some- 

 times one after the other, — when, among the Hyperina, 

 a simple foot becomes a chela in Flironima and a chela 

 a simple foot in Brachtjscelus, &c. 



And yet, according to the teaching of the school, it is 

 precisely in youth, precisely in the course of develop- 

 ment, that the " Type " is mostly openly displayed. 

 But let us hear what the Old School has to tell us as to 

 the significance of developmental history, and its rela- 

 tion to comparative anatomy and systematic zoology. 



Let two of its most approved masters speak. 



*' Whilst comparative anatomy," said Johannes Müller, 

 in 1-844, in his lectures upon this science (and the 

 opinions of my memorable teacher were for many 

 years my own), " whilst comparative anatomy shows us 

 the infinitely multifarious formation of the same organ 



