REPORT ON THE CRUSTACEA. MACRURA. 917 



posterior pair of pereiopoda is sufficiently long to be able to reach as far as the first pair 

 of gnathopoda, in mine it Joes not quite reach to the base of the second pair of pereio- 

 poda, and is feeble and very slender. Clans 1 figures this stage, but represents the 

 ultimate pair of legs as being still more feeble than those in the Challenger specimen. 

 And Anton Dohrn 2 figures the pereion with an indication of the position of the second 

 appendage in relation to the nervous system, and shows that the posterior pair is of 

 scarcely less importance than the penultimate or fourth pair of pereiopoda, and is connected 

 with an independent ganglion subequal in size with that of any of the preceding pairs. 



This appears to me to demonstrate that the developmental process is of a more 

 constant growth than is the case in other forms of Macrura. 



Among all the specimens that have been obtained there is not one that can yet 

 with certainty be pronounced to be adult. Yet it is difficult to suppose that from the 

 numbers of animals that have been traced through a consecutive series of stages, from 

 those with two pair of legs up to those with seven — the normal number that exists in 

 the Decapod Crustacea — that any very decided external change can take place at the 

 putting on of the adult features, which appear to consist in having only the several 

 appendages of the pleon fringed ■ with hairs. 



To Anton Dohrn is due the credit of showing the true relations of the Zoea forms to 

 the adult Amphion, and we cannot but admire the candour of Claus, who, after carefully 

 investigating Anton Dohrn's observations and arriving at a distinctly different conclusion, 

 has wound up his Crustaceen-System by the following " Supplementary Eemarks." 



" After the printing of this work was completed I became acquainted with the 

 communication concerning the development of some Palaeozoic Decapoda by R. v. 

 Willemoes Suhru in the February number of the Annals and Magazine of Natural 

 History. 



" This contains some interesting notes about the genera Amphion, Sergestes, and 

 Leucifer, which, had I been acquainted with them earlier, would have induced me to 

 have taken a rather different view in the chapter on Amphion. 



" It is true that my criticism of Dohrn's interpretation of Amphion as an adult 

 animal is in nowise thereby invalidated, and what I have said of the insufficiency of the 

 rudimentary branchiae, of the absence of a fringe of hair to the pleopoda, as well as of the 

 termination of the supposed ovaries on the posterior pair of pereiopoda (concerning the 

 size and form of which we have heard nothing from Dohrn) as proofs of the sexual 

 maturity of Amphion remains unimpeached, as does also the larval nature of the Crustacean 

 described by M. Milne-Edwards under the name of Amphion and characterised by 

 six pairs of divided feet. 



" Willernoes Suhm has expressly stated that he had found among three full- 

 grown Amphions two male individuals, but probably it was in consequence of the 



1 Loc. cit., pi. viii. fig. S, Fs. 2 Loc. cit. pi. xv. fig. 2. sii. 



