14 DEFINITION OF THE TERM INSECT. 
imperfection of their senses, return again to the Acrita, 
though connected with the Vertebrata by having a heart 
and circulation. 
His next set of circles shows the sub-division of these 
five sub-kingdoms into classes—Thus : 
MOLLUSCA 
TULA 
qsvary 
Agastrvit 
ACRITA 
VERTEBRATA 
SURI Q DI: 
~~ 
ULOPHULSTAQVIIDIA IY) JO 
Ruatantes, 
Fistulida 
TEchinidaj€rustacea 
RADIATA 
CIRKRIPEDA 
In this scheme the osculant classes are those placed 
between the circles. In the Mollusca circle two classes 
are still wanting to complete the quinary arrangement 
of that sub-kingdom. Iam not sufficiently conversant 
