iv. 5. lOi 



All the Testacea, then, those that have not been mentioned as 

 well as those that have, agree as stated in possessing a mouth ^^ 

 with the tongue-like body, a stomach, and a vent ; but they differ 

 from each other in the positions and proportions of these parts. 

 The details, however, of these differences must be looked for in 

 the Researches concerning Animals and the treatises on Anatomy. 

 For while there are some points which can be made clear by 

 verbal description there are others which are more suited for 

 ocular demonstration.^* 



Peculiar among the Testacea are the Echini and the animals 

 known as Ascidians.^ The Echini have five teeth,^ and in the 

 centre of these the fleshy body,'"'^ which is common to all the 

 animals we have been discussing. Immediately after this comes 

 a gullet, and then a stomach, divided into a number of separate 

 compartments, which look like so many distinct stomachs ; for 

 the cavities are separate, and each contains residual matter. They 

 are all however connected with one and the same oesophagus, and 

 they all end in one and the same vent.^ There is nothing, with 

 the exception of the stomach, of a fleshy character, as has already 

 been stated. All that can be seen are the so-called ova,^^ of which 

 there are several, contained each in a separate membrane, and 

 certain black bodies which have got no name, and which, beginning 

 at the animal's mouth, are scattered round its body here and there 

 profusely.*" Of these Echini there are many different species, and 

 in all of them the parts mentioned are to be found. It is not 

 however in every kind that the so-called ova are edible. Neither 

 do these attain to any size in any other species than those which 

 are found in shallow water.*' A similar distinction may be made 

 generally in the case of all Testacea. For there is a great 

 difference in the edible qualities of the flesh of different kinds; 

 and in some, moreover, the residual substance known as the mecon*^ 

 is good for food, while in others it is uneatable. This mecon in 

 the turbinated genera is lodged in the spiral part of the shell, 

 while in univalves, such as limpets, it occupies the apex, and 

 in bivalves is placed near the hinge. In these bivalves the so- 

 called ovum lies on the right ; while on the opposite side is the 

 vent.*3 The former is incorrectly termed ovum,** for it merely 

 corresponds to what in well-fed sanguineous animals is fat ; and 

 thus it is that it only makes its appearance in Testacea at those 

 seasons of the year when they are in good condition, namely spring 

 680 a. 



