regards their means of relation with the external 
world. Having as yet no ganglia developed 
sufficiently important, from their size or situa- 
tion, to merit the title of brains, or fit to be 
regarded as const.tuting a common sensorium, 
whereunto information derived from remote 
rts of the body may be conveyed, localized 
instruments of sensation would be as yet super- 
fluous, and consequently, with the exception 
of the generally diffused sense of touch which, 
from its extreme delicacy, seems in these 
lowest forms of existence to supply to a 
 €ertain extent the deficiency of other means of 
_ perception, instruments of sensation are not 
_ as yet conferred. The presence of a localized 
‘organ of sense, analogous to an eye or an ear, 
‘must obviously be useless to a creature pos- 
sessed of no sensorial centre. to which informa- 
tion, derived through the medium of that sense, 
_ may be transmitted, and organs of the higher 
‘Senses are, therefore, as yet entirely wanting 
throughout the Nematonerurose division of 
the animal kingdom,* as, @ fortiori, they are 
glasses. In like manner the existence of 
ternal locomotive members, moved by any 
‘powerful or elaborately constructed muscular 
_ apparatus, is not to be expected in animals that 
possess not ganglia capable of presiding over 
_.., muscular motion. Limbs, there- 
fore, properly so called, are not as yet de- 
_ Yeloped; and, if in some of the most perfect 
_ Epizoa, the rudiments of such structures be- 
_ come apparent, it is only because the animals 
ein them are so nearly allied to the 
_ Articulata, in their general structure, that the 
‘ervous ganglia in them are beginning to be 
developed, and thus they can only be looked 
bon as the transition steps leading by an 
almost imperceptible gradation from one great 
_ type of animal organism to another of a more 
_ @levated character. 
Im the Arricurata (Iomocancirata, 
Owen), brains, or ruling ganglionic centres, for 
___ the first time make their appearance in a suffi- 
_Gient state of development to correspond with 
_ rgans of sense of a localized character, or to 
_ Allimate systems of muscles adapted to wield 
_ locomotive limbs, and combine complex ac- 
tions now essentially connected with the more 
_ perfect attributes bestowed on forms of life 
__ €apable of more extensive re'ations with sur- 
“Pounding objects. Still, however, an exact 
correspondence exists between the progressive 
_ €xpansion of the nervous centres and the gradual 
ix 
- 
~ 
__* In laying this down as an important physiolo- 
cal axiom, a few words of explanation will be 
equired by those, who, adopting Ehrenberg’s 
views, regard the red spots observable upon nume- 
ia Animalcules and Zoophytes as being the eyes 
of those creatures. ‘That many species of such 
animals possess red spots occupying definite posi- 
‘fons upon different parts of their bodies, no one 
will be disposed to deny who has paid the slightest 
attention to their economy and organization; but 
that these red spots are eyes, we think, for the 
feasons above stated, may reasonably be doubted, 
more especially as it has not even been proved by 
| observation or experiment that they possess either 
the Stracture, or the functions of any visual appa- 
fatus, with which we are acquainted. 
MUSCULAR SYSTEM. 
necessarily deficient throughout the AcriTE - 
531 
appearance of limbs moved by a distinct mus- 
cular apparatus, which become progressively 
superadded to the annulose body or trunk of 
the articulated animal, and in precisely the 
same manner does the advancement of the 
nervous system from a less perfect to a more 
concentrated condition evidently precede the 
appearance of external appendages, subservient 
to the exercise of more exalted powers of sen- 
sation, or increased capabilities of locomotion. 
The humb!estannulose forms, as for example the 
Leech and the Earthworm, possessing, as they 
do, a nervous system consisting of an extended 
series of numerous pairs of feeble ganglia, none 
of which are as yet sufficiently potent to con- 
trol any complex muscular apparatus, or to 
appreciate impressions derived from without with 
much nicety or precision,are necessarily deprived 
of outward limbs, or complicated instruments 
of sense ; their soft and flexible integument is 
unequal to sustain any jointed members what- 
ever, and the first rude vestiges of simple eyes, 
ocelli, are all that can be allowed for the pur- 
poses of vision. By degrees the nervous gan- 
glia becoming fewer in number as they coalesce 
into larger and proportionately more energetic 
masses, the moving organs of the body become 
perfected in the same ratio; limbs, almost 
impotent as yet, but sti!l sketching out the arti- 
culated legs hereafter to be perfected, make their 
appearance, and the apodous Annelidan, the 
humble inhabitant of the water, is promoted 
to a terrestrial existence ; jointed feet at length 
become appended to the segments of the still 
worm-like body, small and feeble at first, as in 
the Iudlus terrestris and the other vegetable- 
eating Myrrapops, but speedily, in proportion 
as the individual segments of the body become 
enlarged and strengthened, and the motor gan- 
glia accuire increased energy, assuming larger 
dimensions and greater perfection of structure, 
until the annulose anima! attains the strength 
and activity of the carnivorous Scolopendra, 
and becomes fitted for a life of rapme and 
destruction. 
Advancing from the Scolopendra, which as 
yet is only able to creep upon the surface of 
the ground, we are at length conducted to the 
far more active and highly gifted races of 
Insects, properly so called, in which the de- 
velopment and perfection of the muscular sys- 
tem is advanced to a condition adapting these 
wonderful little beings to an aerial existence, 
and in making the transition from Myriapod 
to the Insect the carrying out of the same 
great law is most obviously and conspicuously 
illustrated. The nervous ganglia, still nume- 
rous and proportionately feeble even in the 
Scolopendra, become in the aerial insect reduced 
in number until they are collected into a few 
large and potent masses; senses of a wonder- 
fully exalted description, correspondent with 
the increased size of the encephalic ganglia, 
replace the simpler organs of the less exalted 
Articulata ; those segments of the body where- 
unto locomotive members are appended coalesce 
and become fused together into a dense and 
strong thoracic armour able to sustain the vio- 
lent efforts of the powerful muscles now re- 
2M 2 
