The brain of Acipenser. Dan 
nucleus anterior ventralis. The ascending fibres which arise in the 
nucleus dorsalis thalami end in the frontal part of the hemisphere; 
those from the nucleus dorsalis et anterior ventralis end in the 
caudatum ; those from the isthmus or medulla end in the putamen; 
and those from the nucleus entopeduncularis end in the striatum. 
F. Mayer (97) describes fibres in Ammocoetes from the striatum 
to the medulla (partly direct, partly crossed in the anterior com- 
missure) and to the infundibular region. Ascending fibres from the 
hypothalamus end in the striatum and the cortex. In Mammals 
(KÖLLIKER, 96, p. 621) ande fibres run from the nuclei lenti- 
_formis and caudatus. 
Few parts of the brain present a more constant structure through- 
out the Vertebrate series than does the corpus striatum. It every- 
where consists of both I and II type cells, in lower Vertebrates 
imperfectly separated into two nuclei, in higher Vertebrates divided 
into several nuclei in which the distribution of II type cells is not 
fully known. In lower forms the centripetal fibres come from the 
hypothalamus, olfactory lobe (cf. page 230 ff. below), and from 
the cortex. These fibres all enter the nucleus of II type cells, 
‚ epistriatum, by which the impulses are widely distributed among the 
cells of the striatum proper. In this way all the impulses entering 
the corpus striatum, whether olfactory or other, are likely to produce 
similar motor reactions. It appears that the corpus striatum in 
lower Vertebrates has simple functions connected with the first two 
sensory nerves. In higher forms it comes to receive fibres from 
lower sensory centers in addition to those from the olfactory and 
optic nuclei, and from the earliest appearance of the cortex the 
corpus striatum receives fibres from it. In fishes the corpus striatum 
exercises no “higher” functions than those of other parts of the 
brain. In higher forms it comes more under the influence of the 
cortex and forms a part of a more highly organized apparatus which 
we usually designate by the name of cerebrum. 
The few experimental investigations upon the physiology of the 
fore brain known to me tend to bear out this interpretation. STEINER 
(86) found that a fish (Squalus) whose fore brain had been removed, 
moved about and remained quiet by turns, avoided obstacles, saw, 
ate worms, refused twine of the size of a worm, etc. Experiments 
performed by THORNDIKE (99) upon the ability of fishes to learn paths 
to places where food has been found, indicate considerable powers 
of motor memory. In the light of STEINERS experiments it does 
Ie 
