AND DEVELOPMENT OF MELOÉ. ~ 183 
tions, changes which constitute it the true skeleton of the insect. The alterations which 
the body undergoes in form are not accidental results of the actions of the muscles, 
but depend in each species on definite unvarying geometrical principles of force and rela- 
tion. Portions of the tegument which give attachment to muscles are folded inwards in 
the head and thorax, and becoming solidified constitute a rudimentary internal skeleton, 
some parts of which merely give attachment to muscles, whilst others, as in the Verte- 
brata, inclose and protect the nervous system. These I shall hereafter examine with the 
dermo-skeleton of the imago. 
EXPLANATION OF THE PLATE. 
Tas. XX. 
Fig. 1. The young Melo a few days after it has left the egg, highly magnified to show the structure of the 
organs of vision, a; situation of the spiracles, 4,4; form of the tarsi, c, c, and caudal styles, d;. 
and internal muscular structure as seen by transmitted light. 
Fig. 2. Inferior surface of the Melo? larva, showing the structure of the pectoral and abdominal portion 
of the tegument. 
Fig. 3. Melo? larva seen from above by transmitted light, and showing its brain and alimentary canal. 
Fig. 4. A portion of the tegument highly magnified, showing its hexagonal cellæform structure. 
Fig. 5. One of the abdominal spiracles magnified, showing the tegumentary cells with irregular granular 
nuclei. 
Fig. 6. One of the antennz, highly magnified. 
Fig. 7. A dermal spine or hair, originating from the nucleus of a single cell, highly magnified. 
Fig. 8. Portion of tegument showing two layers of cells, the deeper-seated with their nuclei divided and 
in the course of reproduction. 
Fig. 9. The large or thoracic spiracles. 
Fig. 10. The eye of the larva, magnified, showing the cornea formed of tegumentary cells, with the single 
central ocellus. 
Fig. 11. View of the side of the head of the larva. | 
Fig. 12. One of the tarsi, showing the articulated spines at the sides of the true claw. . 
Fig. 13. The full-grown or pseudo-larva, with its limbs reduced to tubercles preparatory to change to a 
; nymph. 
Fig. 14. Skin of the full-grown larva, showing the microscopic hairs developed from the nuclei of cells. 
Fig. 15. The nymph at the period of throwing off the pseudo-larva covering, with its limbs becoming 
. A rapidly enlarged. 
Fig. 16. The fully-formed nymph. - 
