20 BRITISH ENTOMOSTRACA. 



respective works ; and a good account of the circulation 

 of the blood has been given by Gaecle* and Berthold.t 

 For the fullest account, however, of the anatomy and 

 physiology of the Apus, since Schceffer's time, we are 

 indebted to Ernest G. Zaddach, who published a thesis 

 at Bonn in 1841, containing many most interesting par- 

 ticulars of the historv of this curious animal, j 



j 



Anatomy and Physiology, 8fc. The body of the animal 

 is almost completely concealed by the carapace, which is 

 very large, oval -shaped, and covers the head and thorax 

 like a shield. It is rounded anteriorly, and deeply 

 notched at its hinder part. On the back of the cara- 

 pace, more especially towards the posterior extremity, we 

 see a slight keel, which, as it approaches towards the 

 anterior end, divides right and left, into a sort of fork, 

 indicating there the division into cephalic and thoracic 

 portions. The cephalic portion is the smaller of the two, 

 and it is to this portion alone that the body of the animal 

 is strongly connected ; a muscle attaching it just where 

 the first articulation of the thorax takes place, to one point 

 in the centre of its under surface. The thoracic portion 

 covers the thorax and abdomen, without adhering to them 

 at all, except by a fine membrane, which is continued 

 from the point of attachment, and spreads over the whole 

 internal surface of the carapace. The upper surface is 

 convex, while underneath it is concave ; its substance is 

 of a horny nature, and not calcareous, is tough and ex- 

 tremely flexible, and possesses considerable elasticity. On 

 the lateral part of each side, (t. I, f. //), we see a 

 number of well-nmrked lines running obliquely, in an 

 arched form, and being rcflexed. These, according to 

 Zaddach, are canals, and were pointed out by Gaede and 



* Beitriigc zur Anatomic der Insecteii, Wiedcmann's Zoologisches Ma- 

 Kfi/.in, L817. 



t Isis, L830. 



J DC Apodi* fancriformis ; Schreff., Anatomc et ITistoria cvolutionis. 

 Bonnac, 1841. 



