62 The American Naturakst. (January, 
nid. (The fatal number żŘkirteen seems unfortunate just at present—see 
Dohrn!) Then follows a lengthy comparison between the vagus of the 
vertebrate and a series of nerves from the posterior part of the thoracic 
cord, and a comparison between the eyes of the two groups. The 
cranial flexure of vertebrates is entirely explained in the relationship 
of the supracesophageal ganglion (fore- and mid-brain) of the 
scorpion to the thoracic ganglia. ‘The notochord finds its homologue 
in the ‘‘median furrow’’ of Arthropods, which comes from the 
ectoderm, and the support of this homology is found forthwith in our 
ignorance of the origin of the vertebrate cord! ‘‘ Only a strong faith 
in enteric diverticula, and in the red, white and blue gastrules of 
embryological treatises, can lead one to the belief in the entodermic 
origin of the notochord. On the other hand, its growth at both ends 
from superficial cells, and the manner in which it is frequently wedged 
in between the nerve cords, indicate its ectodermic origin.’ This is 
an excellent example of the author’s scientific state of mind in treating 
so important a question as the origin of the vertebrates ! 
The gill-slits come from the rudimentary nephridia of the thorax, 
and somehow—it doesn’t matter much, since they must—connect 
secondarily with the digestive tract. 
The fossil fish Pterichthys probably shows the transitional form be- 
tween Limulus and the vertebrates. The mouth of the latter group 
is a new affair, coming from a dorsal sucking organ of our ancestors, 
and our other Limulus-mouth has long since disappeared. 
Our views of gastrula and blastopore must be rejected, and newer 
ideas received, which will show a wonderful similarity between Arach- 
nids and vertebrates. 
Gaskell, in a former paper, demonstrated how the nervous system is 
composed of nervous material grouped around a central tube, which 
tube was originally the alimentary Sana „= an glad ate aie present 
paper shows, he thinks, that the lowest vertebrate nervous s Ammo- 
ceetes) confirms his theory. The old invertebrate pate tract is 
now the central canal of the nerve cord. Of course the vertebrate now 
turns over, and a new digestive tract arose from the gill region of the 
Crustacean (how the author includes Limulus in this process is not yet 
clear to us, for Limulus he includes in his Crustacea). Nor does the 
author, yet a while, explain how a new'mouth arose ; perhaps he has not 
finally settled on a convenient Arthropod organ. The ventricles of 
the vertebrate brain and the canalis centralis of the cord is the in- 
vertebrate ancestor’s digestive tract, and the infundibulum of Ammo- 
cœtes is the old cesophagus and mouth. 
