352 
POPULAR SCIENCE REVIEW. 
Keturuing to the lobster, we may note sundry fundamental 
facts of structure — 
1. The nervous axis is ventral. 
2. The central part of the circulating system is dorsal. 
3. No solid internal structure separates the nervous centres 
from the alimentary canaJ. 
4. The most anterior part of the alimentary canal bends 
towards and traverses the central axis of the nervous system. 
5. The limbs are more than four in number. 
6. There is no portal system. 
7. In development, no visceral clefts appear. 
8. The jaws are modified limbs. 
9. In development the embryo does not present a longitudinal 
median groove. 
In man, on the other hand — 
1. The nervous axis is dorsal. 
2. The central part of the circulating system is ventral. 
3. A solid structure (the vertebral column or spine) separates 
the nervous centres from the alimentary canal. 
4. The most anterior part of the alimentary canal bends away 
from the central axis of the nervous system. 
5. The limbs are not more than four in number. 
6. There is a portal system. 
7. In development visceral arches ” appear separated by 
visceral clefts.” 
8. The jaws are not modified limbs, 
9. In development the embryo presents immediately a lon- 
gitudinal median groove, which becomes the foundation, as it 
were, of the entire organism. 
Now in these nine diversities of condition all crabs, shrimps, 
insects, scorpions, spiders, hundred-legs, and such -like creatures 
agree absolutely with the lobster ; and all beasts, birds, rep- 
tiles, amphibia {i.e. frogs, efts, &c.), and fishes agree absolutely 
with man, and form together with him the great Vertebrate 
primary division of the animal kingdom. The lobster and its 
allies form together the great Annulose primary division of the 
animal kingdom. 
No animal known to exist now, or ever to have existed in 
past times, presents us with any intermediate condition tending 
to bridge over the chasm yawning between the two so diverse 
types of structure. 
Other types exist as distinct perhaps from either as they are 
from each other. One of these may at a future time form the 
subject of another zoological sketch. 
