932 The American Naturalist. [November, 
pharynx; 3, the origin of the notochord. Under these cir- 
cumstances it is inevitable that the whole hypothesis seems 
highly tentative. Patten emphasizes the fact that the brain’ 
and oesophageal commissures of Arachnids form an angle 
with the ventral nerve chain, and he compares this with the 
head bend of Vertebrates, and seeks to homologize the supra- 
oesophageal and suboesophageal nerves with these of Verte- 
brates. After a careful study it seems to me that he fails to 
render these comparisons morphologically justifiable. This 
failure does away with the only important argument offered 
by Patten. 
C. Bateson’s theory that Balanoglossus represents an ances- 
tral type of the Chordata has attracted considerable attention, 
and Wiley apparently considers the theory proven. Bateson 
seeks to demonstrate a close homology between Balanoglossus 
and Amphioxus. Yet according to his own observations the 
structure of Balanoglossus is extremely different in every 
organ and in every part of every organ from what is found in 
Amphioxus, except as regards the pharynx, where there occur 
striking resemblances in the disposition of the gill bars. But 
Spengel has demonstrated that these are resemblances only, 
and that the arrangement of the bars in Balanoglossus is so 
fundamentally different from that in Amphioxus that it is out 
of the question to deduce one from the other. Again, accord- 
ing to Bateson’s observations on the development of Balano- 
glossus, Tornaria is one of the forms least like the embryonic 
lancelet, for it entirely lacks the segmented mesoderm, the 
notochord and elongated medullary plate. Bateson, in my 
opinion, has drawn exactly the reverse of the conclusions as 
to the phylogenetic value of Balanoglossus, which are war- 
ranted by his own published observations. Spengel’s criticisms 
of Bateson’s theory are so conclusive, that it is superfluous to 
go over the ground again. But two points may be briefly 
mentioned, if only to escape the charge of trifling with the 
theory. Buteson lays much emphasis upon a structure, which 
he names the notochord of Balanoglossus; this so-called 
“notochord” is a short diverticulum of the cephalad end of 
the alimentary canal, running into the proboscis; this diver- 
