Dr. J. Young on the Mahcostraca of Aristotle, 249 



an interval, as already described, from the tail. The '^cartilages ^^ 

 are divided into several parts, meaning probably the outer and 

 inner plates of the abdominal feet. These are not only, like the 

 operculum of Carcinus, larger in the female ; but they enlarge 

 towards the end of gestation for the reception of the ova, which 

 are brought to their places by the bent and adpressed tail. The 

 epicalymmata or opercula, as the outer plates of the somites are 

 called, not being able to cover the mass of ova, the incurved tail 

 assists, overlapping them like a lid. The mechanism in Carcinus 

 is not alluded to. 



These animals in spring, and in autumn after generation 

 (H. An. viii. 19. 5), cast a slough like serpents, but not, like 

 them, in one piece, since individuals have been caught with one 

 half of the body soft, the other still hard. This occurs not once, 

 but often : it is said elsewhere to occur both immediately after 

 birth (eudv^ <ycyy6/jL6voL)l and later (v. 15. 6). During the pro- 

 cess they are weak and unwilling to move, concealing themselves 

 till their integuments recover their hardness. 



Sexual distinctions. — These are the presence or absence of 

 pincers, variations in their size when present, the development 

 of spurs on the last pair of feet, the larger size of the abdominal 

 plates in the female. Uncertain as we are as to the exact ani- 

 mals referred to by Aristotle in these observations, their accu- 

 racy, except as to the abdominal plates, cannot be tested. The 

 inequality in size of the pincers of Astacus is rightly shown not 

 to be of sexual value. The female Carcinus is altogether larger 

 than the male; her operculum in particular is broader and 

 rougher. This relation of size to the function of reproduction 

 is also noted among insects. 



Digestive Si/stem. — The presence of teeth ( = the mandibles) 

 in all Malacostraca is stated : in Carcinus they are round, not 

 long. The tongue, or rather its analogue, is mentioned as an 

 essential organ in all animals (De Part. iv. 5). Though stated 

 to be between the teeth, the whole mouth seems elsewhere pos- 

 sessed of the function of taste. 



The stomach follows the mouth, though separated from it, in 

 Carcinus and Carabus, by an oesophagus small in proportion to 

 the size of the body (De Part. iv. 5). The stomach is mem- 

 branous, and provided with teeth at its mouth — an oversight 

 due to the close approximation of the cardiac and pyloric orifices, 

 to the latter of which they properly belong. They are not pre- 

 sent in all Carcini — a doubtful statement. Their purpose is to 

 triturate the food insufficiently acted on by the oral teeth. 

 From the stomach, which in Carcinus is said to be double 

 (though the remark applies equally to the other members of the 

 group), the gut, simple, of equal thickness throughout, passes 



