OR ANIMALS WITHOUT BLOOD. 225 



very short and bit against the proximal end of the outer 

 part. 



Aristotle's statements on this subject are inconsistent, 

 and, in the identification of Karahos, it is best to follow the 

 course adopted by Meyer,* and take the evidence furnished 

 by Aristotle's description as a whole. 



Not less than two species, viz., Homarus vulgaris, the 

 common lobster, and Astacus fluviatilis, the crayfish, are 

 included under the name Astakos. Aristotle clearly gives 

 the following characteristic features, viz., chelae large and 

 unlike in size and form, with sharp marginal spines; four 

 pairs of small legs, of which two pairs are chelate ; antennae 

 much shorter and smoother than in Karahos ; eyes smaller 

 that those of Karahos ; rostrum long, sharp, and rough ; 

 cephalothorax smooth and comparatively soft.t He also 

 says that there are four antennules,t and was apparently 

 unaware that there are really only two, each of which is 

 divided. The crayfish is more particularly referred to in 

 H. A. iv. c. 4, s. 19, where he says: " like the small Astakoi, 

 which are found in rivers," 



That Aristotle's Karkinoi are crabs is clear from his 

 showing that they are decapods, rounded and not elongated, 

 and that they are without tails, such as those of the 

 Karahoi and some other crustaceans. § He also says that 

 the right chela is always, || or generally,^ larger than the left. 

 The right chela is larger than the left one in many crabs, 

 but there are some in which the right and left chelae differ 

 but little, if any, in size, e. g., specimens of Portunus, 

 Geryon, and Thalamita, while there are some in which the 

 left chela is larger than the right, e.g., specimens of Xantho, 

 Ocypoda, and Porcellana. 



The largest crab, Aristotle says, is Mala, with eyes 

 close together, and with very thin legs ; this crab lives 

 out in the sea.** It is probable that this is one of the 

 spider crabs. 



Aristotle clearly refers to some species of Ocypoda, or 

 swift land crab, for he says that, on the coast of Phcenicia, 

 there are crabs called Hippeis, or horsemen, because they 



* Aristoteles Thierhunde, Berlin, 1855, pp. 240. 

 t H. A. iv. c. 2, ss. 6-9 ; P. A. iv. c. 8, 684a. 



I H. A. iv. c. 2, s. 8. 



§ H. A. iv. c. 2, ss. 3 and 4 ; P. A. iv. c. 8, 6a4a. 



II P. A. iv. c. 8, 684a. H H. A. iv. c. 3, s. 1. 

 ** H. A. iv. c. 2, s. 2, iv. c. 3, s. 2 ; P. A. iv. c. 8, 684a. 



Q 



