The brain of Acipenser. 61 
E. bhepome,. brain à. soe ioe 109 2229 
a) Nucor Ni, 1: RR i eG ML LS 139 
1. Corpus striatum wir GOs TROUS ee OL 139 
2. Secondary olfactory nuclei let Kenn 140.284 
2 Cie > Re 
b'Akibre tracts, ~....,.. Si lg eras. ean Marya ets 144 
1. Tractus strio- thalamicus Be ee te en 144 
2. Tractus olfacto-habenularis . . . . . . 145 
F. Olfactory Lobes . . a N) kate ee aS 
a) Cells of the olfactory lobe Pe Sith yeh CU 146 
MO laetory ‚frhres; NC NC 151 
c) Glomeruli . . st RM LE à: 154 
d) Tractus olfactorius. . . Be u, 102.024 
2. Interpretation. Review of Literature Bat 155 
The arrangement of matter in this part follows that in the de- 
scriptive part so closely that I have given the references to 
pages for both parts in the above outline. The higher 
numerals refer to the theoretical part. 
HOFESummary,Eof results: 2. „'. ee 239 
I. Introduction. 
The present research, begun in the fall of 1895, is an attempt 
at acomplete study by modern methods of the brain of a lower 
vertebrate (Acipenser rubicundus LE SEUR). It was hoped that the 
full study of a single somewhat generalized brain would be of serv- 
ice in the solution of problems in the morphology of the higher 
vertebrate brain. 
Material and Methods. 
The greater part of the work was done on the brains of young 
fish 25 to 40 cm in length. Of such brains I have two series of 
frontal (transverse) sections stained with DELAFIELD’s haematoxylin, 
and seventeen series by the GOLGI method in various planes. In ad- 
dition, I hardened a large number of brains of adult fish (one to two 
meters in length). Of these I have one series of sagittal sections 
stained with methylene blue and acid fuchsin, and nine partial 
series by the method of GoLGI which were useful for the study of 
the fore brain and olfactory lobes. Several of the large brains 
were used for dissections, and the photographs of the entire brain 
were made from two of these. 
The seventeen series of GOLGI sections of the small brains con- 
stitute the chief material on wich the study has been made. In making 
