98 HISTOEY OF CRUSTACEA. CHAP. X. 



Lobster with Schizopodal feet ; Paltemon, like the Crabs, 

 as a Zoe'a ; and Peneus, like the Cirripedes, as a Nau- 

 plius, and when, still, within this same sub-order Ma- 

 crura, Palinurus, My sis and Euphausia 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 Phronima and a chela 

 a simple foot in Brachyscelus, &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 Miiller, 

 in 1844, 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 



