168 MR. NEWPORT ON THE NATURAL HISTORY, ANATOMY, 



many of the Invertebrata, and of which the subject of our present inquiry, Meloe, is a 

 striking exemplification. 



It is in the tegument itself that every change of form in the external parts of the 

 body is commenced ; first in slight reduplications of this tissue to form segments ; next in 

 the aggregation or partial coalescence of these into particular sets, or regions ; and lastly 

 in the hypertrophy or excessive growth of the tegument, at definite points, which produces 

 elevations or protrusions from the uniform surface, and which protrusions constitute the 

 origin of the future appendages. It is by the continuation of these processes of growth 

 in the formation of the animal, — and which processes take place by means of the enlarge- 

 ment and repeated fissiparous division of the nuclei of the cells of which the whole tissue is 

 originally composed, and by the further development of these into cells, as I shall elsewhere 

 show, — that the entire growth of the tegument, from the earliest period of its formation in 

 the ovum to its completion in the adult animal, is effected. Portions of this tissue, consoli- 

 dated by changes which ensue in the function of the nuclei of some of the layers of cells, 

 constitute the hardened dermo-skeleton, which protects and gives support to the internal 

 structures of the insect. The nuclei of these cells, instead of continuing to be multiplied 

 by repeated subdivision into separate organisms, which in their turn are evolved into cells, 

 seem more and more to lose their juvenescence, or reproductive power, in proportion as 

 they are made to approach the exterior of the body by the growth of other layers of cells 

 beneath them. They then gradually become altered in function, and the forces of growth 

 being diminished in a ratio inverse to their maturity, earthy constituents are secreted 

 by them in greater proportion than during their previous existence as reproductive bodies. 

 These earthy constituents assume an inorganic, granular, or semi-crystalline form, and 

 constitute the solid material of the hardened skeleton. This process takes place to a greater 

 or less extent throughout the whole period of development of the insect. It commences 

 in some parts even at an early period of the embryo in the ovum, in the solidification of 

 the hard portions of the mandibles. It is this result of change in the function of the 

 nuclei in their full age, and the partial aggregation of their granular contents, which lead 

 to the deciduation of layers of the tegument in the larva. The cells with accumulated 

 earthy matter in their interior cease to be nourished, perish, and become separated from the 

 layers of juvenescent cells beneath them in the vigour of growth ; and are ruptured and 

 thrown off as an entire covering when they retard the further expansion of these and of 

 the whole body. The deciduated cells do not differ, other than in these circumstances, 

 from those which are still in the course of enlargement. 



The earthy materials thus deposited in the dermo-skeleton of insects have been found 

 by Odier*, Lassaignet, Mr. Children J and others, to consist chiefly of phosphate of lime, 

 with carbonate of potass, some carbonate of lime, and a little phosphate of iron, with, in 

 some species, silica, magnesia and a trace of manganese. This composition led me, ten years 

 ago§, to describe the dermo-skeleton of insects as "an imperfectly developed condition of 



* Memoires de la Societe d'Hist. Nat. de Paris, torn. i. 



f In Straus Durckheim's Considerations Generales sur 1' Anatomie Comparee des Animaux Articules, 4to. 1 828, p. 33. 



% Zoological Journal, vol. i. 1824, p. 115. 



§ Article " Insecta," Cyclopaedia of Anatomy, par. xviii. October 1839, vol. ii. p. 882. 



