1881 .| Comparative Neurology. 107 
The slight development of the superior ganglia in Brachiopoda 
is correlated with higher sensory organs, and Gegenbaur, p. 310, 
notices that the nerves for the arms are probably given off from 
the ventral ganglia, a condition which I suspect is more common 
than usually thought to be the case, due to the want of differen- 
tiation between alimentary and locomotor parts, so far at least as 
central innervation is concerned. “In the Mollusca the visceral 
ganglia are not only of importance, as forming a part of the gen- 
eral nervous system, but they may also fuse with the cerebral 
ganglia, owing to the gradual shortening of their commissures. 
New and primitively peripherally placed parts are thereby added 
on to the central organs, and it becomes a matter of doubt whether 
or no these ganglia, which formerly belonged to the visceral ner- 
vous system should still be regarded as belonging to it.” —Gegen- 
baur, p. 344. 
The development of the nervous system appears to have pro- 
ceeded as follows 
PRIMARY. 
Intestinal—Circulatory and visceral, cardiac. 
SECONDARY. 
Respiratory—Special tactile locomotory, auditory, optic, or 
optic and next auditory. 
Antennal special tactile from which auditory in some ; (olfactory 
not certain in Invertebrata, possibly in Cephalopoda. Jn Verte- 
brata originate highest secondary and tertiary). 
The progression of faculties intermingle and a branch sense 
appears often to develop indifferently from one or other trunk, as 
while respiratory may give rise to the tactile for locomotion, and 
audition follows upon this, the antennal for gustatory purposes 
May originate the auditory, while locomotor tagtile may be 
developed separately. 
NERVOUS ORGANIZATION OF INVERTEBRATA. 
1. Protozoa—Not perceptibly differentiated. 
2. Celenterates—Rudimentary primary. 
3. Vermes. Secondary appears and becomes highly 
4. Echinodermata. developed. Often fused with primary. 
Secondary well developed. In Insecta 
5. Arthropoda. the primary quantitatively developed. 
Tertiary pronounced in bee, 
