174 MR. NEWPORT ON THE NATURAL HISTORY, ANATOMY, 



into the prothorax. The dorsal region of the body in the young Meloe, as in the very 

 young larvae of most of the Artieulata, is not so far advanced in its development as the 

 sternal and ventral, at the period when the insect leaves the ovum; owing to its being the last 

 portion that is formed. Consequently we find the insertions of the legs in the young, at a 

 relatively greater distance from the median line of the sternal surface than in the imago. 

 The legs are as it were appendages of the sides of the body ; while the respiratory orifices, 

 which properly belong to the membrane that connects the dorsal with the ventral surface 

 in the perfect insect, actually exist in the young Meloe at the sides of the dorsal region. 

 But in proportion as the growth of the body is advanced the relative dimensions and posi- 

 tion of these parts are changed. The growth of the sternal surface, after the insect has 

 left the ovum, does not proceed so rapidly, and is not carried to so great an extent as that 

 of the dorsal ; the result of which is that the coxae of the legs become relatively more and 

 more nearly approximated to the median line, and are transferred to the under surface of 

 the body in the perfect insect. The spiracles also, from a like cause, are changed in their 

 form and position, and are gradually removed from the dorsal to the lateral surface by 

 the more rapid growth and extension of the former. The dorsal region itself is widened, 

 is rendered more convex, and ultimately becomes the most voluminous portion of the 

 whole body. These facts of development are common to all insects, and are well-indicated 

 in the structure of the adult larva of Meloe, in which the entire form of the insect 

 is completely altered by this difference in the relative development of its parts. 



Read April 18th, 1848. 



2. Tegument of the Full-grown or Pseudo-larva. 



Every natural change in the animal body, whether of structure, of function, or of 

 instinct, takes place by regular and inevitable gradations, all of which seem to depend on 

 immutable laws of organization. No strongly-marked transition from one condition to 

 another, whether in character, in form, or in degree, ever occurs by sudden or violent 

 alterations, without deranging the body, the organ, the function, or the instinct that is 

 subject to such change, and inducing its permanent impairment, or premature annihilation. 



Newton, the pride of physical science, was as fully impressed with these truths, with 

 regard to the animal body, as with their correlatives which regulate the universe itself, 

 when — pondering on the laws which he was then proving govern light and space — he 

 wrote the following words : — " Idemque dici possit de uniformitate ilia, quae est in cor- 

 poribus animalium*." These views with regard to the uniformity of structure and develop- 

 ment in organized beings, — originally glanced at by Malpighi in his anatomy of the Silk- 

 worm in 1669 1, and dwelt on to some extent by our own almost forgotten countryman 

 Dr. Willis, in 1682 %, — have since been amply demonstrated by the illustrious Geoffroy Saint 

 Hilaire§ and his numerous followers ; and it is now my humble endeavour still further to 



* Optics. Edit. S. Clarke, p. 346. 4to. 1706. 



f Dissertatio epistolica de Bombyce ; Societati Regiee Londini dicata. 4to. Londini, 1669. 

 % Opera Omnia. 4to. 1682. 



§ Philosophie Anatomique des Monstruosites Humaines. 8vo. 1822. Also, Cours de l'Histoire Naturelle des Mam- 

 miferes. 8vo. 1829. 



