170 MR. NEWPORT ON THE NATURAL HISTORY, ANATOMY, 



its mode of development, and in its function, to true bone ; and even as homologous with 

 the external bony skeleton of Chelonian reptiles ; the internal portions of which are similar 

 in structure, as in office, to the internal processes of the tegument in the Articulata. 



But if, for the moment, in deference to the opinions of some physiologists, we were to 

 discard this view of the nature of the tegument, and regard it simply as a dermal covering, 

 we must still look upon it as but one structure, formed of layers of cells in different stages 

 of growth ; and not as composed of distinct tissues, epidermis, mucous layer, and corium, 

 the definite limits of which it is perhaps impossible satisfactorily to indicate. 



When a very young Meloe (Tab. XX. fig. 1) is examined a few days after it has left the 

 egg, its tegument affords a complete demonstration of cellseform structure. The whole tis- 

 sue, if examined under a high power, is then seen to be composed of a uniform layer of 

 irregularly hexagonal cells (fig. 4), which are almost equally distinct in the covering of the 

 head itself as in that of the thoracic or the abdominal segments. In some parts of the tis- 

 sue, as in the more transparent ones near the spiracles (fig. 5), each cell is seen to contain 

 a very delicate, granular, irregularly stellate nucleus, which I regard as corresponding to 

 the cells seen by Platner in the tegument of the Silk- worm. Those cells which are on the 

 surface of the body are of a somewhat quadrangular form, and they are arranged in a 

 more linear direction than those which are deeper seated. Their nuclei are distinctly 

 granulous, and occupy a very large proportion of the interior of the cells. This granular 

 condition of the nuclei exists more especially in the cells of the thoracic segments, and 

 closely resembles that in which, according to Mr. Tomes, true osseous matter is depo- 

 sited in the Vertebrata. The largest of these cells measures about one two-thousandth of 

 an inch in diameter. The cells in the tegument of the limbs are less uniform in structure 

 than those of the body. On the femora they are slightly tuberculous, so that the limbs 

 are a little roughened on their surface ; while on the tibial and tarsal portions they are 

 more elongated and are less distinct. This also is their condition in the antennae (fig. 6). 



The tegument has its own proper appendages in the form of hairs or imperfect spines 

 (fig. 7). Each of these spines projects from the surface of what, at first sight, appears to 

 be a distinct opening in the external layer, but which is an enlarged and altered cell, 

 the size of which, sometimes, is much greater than that of the other cells, and measures 

 nearly one thousandth of an inch. It is circular, with a convex disc, bounded by a distinct 

 margin, and surrounded by the proper cells of the external surface. In its centre is a 

 slight elevation, from which passes out the minute hair or spine, perfectly smooth on its 

 sides, and gradually diminishing in size from its base to its apex. When closely examined 

 each spine is found to be hollow from one extremity to the other. Prom its central ori- 

 gination, in a distinct structure homologous with that of the other cells of the tegument, 

 I am induced to regard the spine, as, primarily, an excessive growth of the nucleus of a 

 cell, everted and developed outwards as a single structure instead of being subdivided into 

 nucleoli, or of secreting earthy matter, as in other instances, its cavity being continuous 

 with a passage in the layers of cells beneath. 



The mode in which the tegument is developed after the insect has left the egg, is 

 similar, as I have already stated, to that of its origination in the blastoderma. I have 

 distinctly ascertained this fact in the young Meloe. It commences in the formation of an 





