122 HISTOKY OF CRUSTACEA. CHAP. XII. 



CHAPTEK XII. 



PROGRESS OF EVOLUTION IN CRUSTACEA. 



ACCORDING to all the characters established in the last 

 paragraph, the Prawn that we traced from the Nauplius 

 through states analogous to Zoea and My sis to the form 

 of a Macrurous Crustacean appears at present to be the 

 animal, which in the section of the higher Crustacea 

 (Malacostraca) furnishes the truest and most complete 

 indications of its primitive history. That it is the most 

 complete is at once evident. That it is the truest must 

 be assumed, in the first place, because the mode of life 

 of the various ages is less different than in the majority 

 of the other Podophthalma ; for from the Nauplius to 

 the young Prawn they were found swimming freely in 

 the sea, whilst Crabs, Porcellance, the Tatuira, Squilla, 

 and many Macrura, when adult usually reside under 

 stones, in the clefts of rocks, holes in the earth, subter- 

 ranean galleries, sand, &c., not to mention other devia- 

 tions in habits such as are presented by the Hermit 

 Crabs, Pinnotheres, &o., and secondly and especially 

 because the peculiarities which distinguish the Zoe'a of 

 this species particularly from other Zoeae (the employ- 

 ment of the anterior limbs for swimming, the furcate 

 tail, the simple heart, the deficiency of the paired eyes 



