20 
BRITISH ENTOMOSTRACA. 
respective works ; and a good account of the circulation 
of the blood has been given by Gaede* and Berthold.f 
For the fullest account, however, of the anatomy and 
physiology of the Apus, since Schoeffer’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 history of this curious animal. 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. h), we see a 
number of well-marked lines running obliquely, in an 
arched form, and being reflexed. These, according to 
Zaddach, are canals, and were pointed out by Gaede and 
* Beitrage zur Anatomie der Insecten, Wiedemann’s Zoologisclies Ma- 
gazin, 1817. 
f Isis, 1830. 
X Be Apodis cancriformis ; Schceff., Anatome et Historia evolutionis. 
Bonnse, 1841. 
