Chap. XXVII. OF PANGENESIS. 363 



parent-form, as with, the larva? of Cecidornyia, or may differ 

 to an astonishing degree, as with many parasitic worms and 

 jelly-fishes; but this does not make any essential difference 

 in the process, any more than the greatness or abruptness of 

 the change in the metamorphoses of insects. 



The whole cpiestion of development is of great importance 

 for our present subject. When an organ, the eye, for instance, 

 is metagenetically formed in a part of the body where during 

 the previous stage of development no eye existed, we must 

 look at it as a new and independent growth. The absolute 

 independence of new and old structures, although corre- 

 sponding in structure and function, is still more obvious when 

 several individuals are formed within a previous form, as in 

 the cases of alternate generation. The same important prin- 

 ciple probably comes largely into play even in the case of 

 apparently continuous growth, as we shall see when we con- 

 sider the inheritance of modifications at corresponding ages. 



We are led to the same conclusion, namely, the independ- 

 ence of parts successively developed, by another and quite 

 distinct group of facts. It is well known that many animals 

 belonging to the same order, and therefore not differing widely 

 from each other, pass through an extremely different course 

 of development. Thus certain beetles, not in any way re- 

 markably different from others of the same order, undergo 

 what has been called a hyper-metamorphosis — that is, they 

 pass through an early stage wholly different from the ordinary 

 grub-like larva. In the same sub-order of crabs, namely, the 

 Macroura, as Fritz Muller remarks, the river cray-fish is 

 hatched under the same form which it ever afterwards retains ; 

 the young lobster has divided legs, like a Mysis ; the Palsemon 

 appears under the form of a Zoea, and Peneus under the 

 Nauplius-form ; and how wonderfully these larval forms differ 

 from one another, is known to every naturalist. 31 Some 

 other crustaceans, as the same author observes, start from the 

 same point and arrive at nearly the same end, but in the 



31 Fritz Midler's ' Fur Darwin,' Nat.,' 2nd series, Zoolog., torn. iii. p. 



1864, s. 65, 71. The highest 322) on the difference in the meta- 



authority on crustaceans, Prof. Milne- morphosis of closely-allied genera. 

 Edwards, insists ('Annal. des Sci. 



