430 REVIEWS. 
den and abrupt nature of the changes spes ch insects undergo. Isay“ Semra oe 
cause the changes in the internal organs, though rapid, are in reality gradual; and e 
- a — serernal form, tho: ou, pre = metamorphosis ad take fi a few sere be 
re, of the curtain; and the 
n , perhaps, weeks before. 
Swammerdam, indeed, supposed (and his view was ado opte ed by Kirby and Spence) that 
the tear contained within itself “t of the future butterfly, enclosed in what will 
be t ase of which is itself cae in the three or more skins, one over the 
other, that will herpes cover the a.” This is entirely a mistake; e 
osai if yod exam mine a shortly belie k becomes a pupa, you bee find biae the skin 
ithi y be traced. In the e mann you ex- 
min t to disclose the butterfly, you will pies chee: piian soft 
oe and “imperfect, reg still easily re ae coment eh g more or less loosely within the 
kin. 
‘Oat fundam maa -e between an insect haar a vertebrate —- is, — i 
scles 
ny 
man He ence the necessity for the hard and horny dermal investment of 
skeleton, in oea, no se skeleton exists. They have no bones, and their muscles are 
ed Enr 
S n skin. 
Moreover the result is, that without a change of skin a dn of form is impossible. 
The citi, or horny substance, forming the outside of an insect, is formed by a layer of 
cells "e benea th it, and, once formed, cannot be altered. From this it follows, that 
May AUCO p anied a change of skin. 
In some « as for instance in Chloeon, silts change of skin is a tinned 
1l change of form, and thus the perfect insect is more or less gradually evolved. tn 
others, as for instance in Cate llars, several changes skin take place aben any 
alteration of form, and the change, instead of being roa over many, is confined to the 
two moults, 
ory litt} im The mouth of 
the Caterpillar is provided with a pair of strong jaws, fitted to eat leaves; and the digest- 
ive organs are adapted for this kind of food. 
On the contrary, the mouth of the butterfly is suctorial; it has a long proboscis, beau- 
indeed, only an embarrassment to the larva. Th ive o ted for 
assimilation, not aia but of honey. Now it is evident that if the mouth-parts of 
the larva were gradually metamorphosed into those of the perfect insect, through a num- 
ber of small changes, EPER in the mean time be unable to feed, and liable to 
poran of starvation in the midst o of plen 
whic 
the changes are gradual, the mouth of te so-called larva resembles that of the poe 
insect, and th 
= 
Simil: id sb ri PER + 1. etate— 
o E voni pupa state 
iod of d like qui which mis one of the most striking ch 
teristics of insect-metamorphosis. The comparative q of the pupa is mainly 
nwin e. +h mts 
_ In n the'chrysalis of a butterfly, for instance, not only, bond has been already mentioned, 
ee ation: and even 
chao 
if they were in a condition fay ourable to patios py gassing gen or the 
oneal eee are regulated, is also in astate of such rapid change that it 
- The conclusi th which T think A h dine and other con- 
si ore id J afoul P ee 
siderations, are: — g 
Ist. That the o 1ce of me > MEP Se e a i > ska oondition 
That the i a a riginal vermi- 
originar v 
frm pes depenas in grent measure on the conditions in which it teak The 
