1881.] Origin and Descent of the Human Brain. 515 
A Teliost, the Zrigla adriatica, affords an example of these 
same enlargements appearing all along the spinal column: 
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(The /ateral fusion also between these ganglia in the head end, 
occurs among the intervertebral in Orthogoriscus mola.) 
Taking a general survey of the piscine and amphibian brains, 
we find, in many, these ganglia well defined as rounded, symmetri- 
cally placed bodies (Lepidosteus, Amblyopsis, Leuciscus), while in 
others these lobes are distorted, by elongation or cramping, in all 
directions (sturgeon, chimzra, sharks), and in still others, some of 
the lobes are pushed below the usual site (cod, herring, perch). 
Of necessity the ventricles must often be partially or wholly 
obliterated, showing the inexpediency of making use of ventricu- 
lar passages in homologizing. 
This crowding together, fusion and distortion of ganglionic 
lobes, obtains throughout animal life, and the olfactory lobe is 
often so closely fused with the prosencephalon as to afford us no 
line of separation. An interesting point in this connection is pre- 
sented by the corpora bigemina, which lie upon the upper surface 
of the brain in reptiles, being succeeded in birds by these bodies be- 
ing thrown down to the sides and base of the brain, crowded 
there by the greater relative size of the superior lobes. 
The intervertebral ganglia which develop on the afferent nerves 
of the higher vetebrates undergo great developinent within the 
cranium, and by lateral crowding together, the median line of sepa- 
ration is obliterated, giving us the large central lobe of the shark 
and birds. Two or more of these ganglia may develop upon the 
Same sensory strand (see Davida, Centralblatt, No. 26). The 
Subsequent lateral lobes of the cerebellum can be resolved either 
into secondary or primary ganglia, or a mixture of both, certainly 
the vagus tubercle of the fox shark is in all essentials the pneu- 
Mogastric lobule of man’s cerebellum, the flocculus. 
Thus it appears that by the pressure together of a nuthber of 
€s€ posterior spinal nerve root swellings a cerebellum has been 
formed, The cerebellum is now generally conceded to be a co- 
ordinator of sensation for cranial sensory nerves, and how can it 
be otherwise from this view? By this coalescence of interverte- 
