270 



PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



is without appendages, form the powerful flipper at the 

 end of the tail for backward darting. Going thence 

 forward, we come to the cephalo- 

 thorax. Here many joints in their 

 dorsal parts are consolidated into 

 a carapace, and their ringed struc- 

 ture is lost, but their entire dis- 

 tinctness is evident in the lower 

 crustaceans and in the embryos 

 of the higher. But observe that 

 it is only the dorsal parts that are 

 consolidated. In the ventral parts 

 the separate rings are distinct, 

 and each has its own pair of 

 jointed appendages greatly en- 

 larged for walking, A/ 1 ,/ 2 ,/ 3 ,/ 4 . 

 These are the five pairs of limbs. 

 Going still forward, we find next 

 three or four pairs modified for 

 the gathering of food. These 

 are called maxillipeds, or jawfeet, 

 md, md', md s The modification is 

 not so great but that their resem- 

 blance to the limbs is obvious. 

 Next come two or three pairs more 

 modified, so as to adapt them for 

 biting. These are the maxilla, or 

 jaws, mx. Next come two pairs 

 of highly modified, greatly elon- 

 gated, and many-jointed append- 

 ages, which are organs of touch 

 and hearing. They are sense ap- 

 pendages. Lastly, a pair of joint- 

 ed appendages, on the ends of 

 which are placed the eyes. Some 





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