7^ CHIKONOMUS PRASINtrS. 



special membrane covering the cells similar to the cuticula of 

 plants." Such is the uniformity of Nature's plan in creatures so 

 widely different. The zona radiata of many ova is, probably, also 

 a phenomenon of this nature. The epithelium of the malpighian 

 tubes consists also of polygonal, granular^ nucleated cells lining 

 the cavity of these organs. That of the small intestine is as 

 inconspicuous as that of the oesophagus, but in the large intestine 

 we again meet with a prominent epitheUal covering, the large 

 nucleated granular cells of which bulge out irregularly between 

 the crossing fibres of the muscular coat. In general, it may be 

 stated, that the cellular elements of the alimentary canal contrast 

 with those of the integument, first by reason of their superior 

 size, and secondly by the granular character of their contents. 



The third coat of the alimentary canal is a very delicate, 

 structureless, basement membrane, upon which the epithelial coat 

 rests, and as such it forms also the investment of the malpighian 

 tubes. We may here remark that in the integument there are 

 three layers, viz., cuticle, hypoderm, and basement membrane; so 

 also in the alimentary canal, there are three layers corresponding 

 thereto, viz., cuticle, epithelium, and basement membrane. I do 

 not know whether this last is to be regarded as a membrana 

 propria, secreted like the cuticle by the epithelial cells, or whether 

 it is a form of connective tissue. ^'^ 



The fourth coat is the muscular one consisting of longitudinal 

 and transverse muscular fibres. It differs much in character in 

 different parts, being scantily represented in the stomach and 

 large intestine, but very thick and prominent in the oesophagus 

 and small intestine. In the stomach and large intestine it forms 

 a loose mesh of delicate fibres crossing at right angles, and 

 leaving square inter-spaces, where the basement membrane 

 bulges out between. In the oesophagus and small intestine, 

 it consists almost, if not exclusively, of transverse fibres ranged 

 side by side, without any interval, round the canal, and is 

 of considerable size. These fibres are shown in Fig. 15, where 



* From the above it appears difficult to avoid the conclusion that the 

 digestive juices in insects have to act upon the food through an interposed 

 cuticular membrane, and that the chyle so prepared must pass through this 

 membrane on its way to the blood. I do not know whether anything has 

 been written on this curious subject, but it is eminently worthy of note. 



