Now we may reverse the position of our subject, and having cut off the wing-cases, which are technically called _teg´mina_, examine the wings. These may be gently unfolded with a needle or a camel’s hair brush, when the longitudinal method of folding will be clearly seen, and the difference of the veining from that of the wings of the Margined Water Beetle will be apparent. A female should also be examined, and the small tegmina cut off, so as to see that not even the rudiments of wings are present. The Cockroach breathes like other adult Insects, and the spiracles are ten in number--two on the thorax and eight on the abdomen. The thoracic spiracles may be pretty readily seen, but those on the abdomen are not so easy to make out. But by cutting away, with a fine pair of scissors, the edges of the plates that cover the upper and under surfaces of the abdomen and the membrane that unites them (Fig. 34), we may discover them as the open ends of small tubes. While dealing with the insect in this fashion, it will be easy to take out a piece of the tracheal tube, which may be compared with Fig. 28. [Illustration: FIG. 34.--Cockroach, showing Spiracles.] The abdomen consists of a series of rings or segments, the exact number of which is rather difficult to decide, from the fact that some are concealed and others altered in form. Dr. Sharp[19] says that ‘it is considered that ten dorsal and ten ventral plates exist, though the latter are not so easily demonstrated as the former.’ In the male, ten above (dorsal) and nine below (ventral), and in the female two less in each case, may be made out without dissection. From the sides of the tenth segment two organs, the _cerci_ (Fig. 35, _a_), are given off, one on each side. These may be distinguished from the styles of the males by their presence in both sexes. Our inch lens will show that each cercus consists of sixteen rings. If we use the half-inch, we shall see that each ring is set with hairs of different lengths. When we have got so far it may be well to compare the structure of a _cercus_ with that of an antenna (p. 67). In each we have a succession of jointed rings giving flexibility to the organ, and the rings in each case are studded with hairs. It has been shown pretty conclusively--and we may verify the experiments--that the antennae are sense-organs. Are we not justified in coming to the conclusion that, since the antennae and the cerci resemble each other in structure, they also resemble each other in function? If the Cockroach receives sensations by means of the antennae, is it not probable that it also receives sensations by means of the cerci?