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connective tissue, except a small pit. The tongue was shortened 
and the copula of the hyoid arch strongly compressed, probably on 
account of the stalk which proceeded exactly in front of the tongue. 
In the lower jaw the genio-hyoid muscle was also strongly compres- 
sed on the left side; otherwise here also little change was noticed. 
What may have been the cause of the abnormal growth and how 
ean this condition have developed? On the former point we must 
remain entirely in the dark. As to the second we may start from 
two suppositions: 1. the eye has descended in a full-grown condition ; 
2. the eye-vesicle already deviated from the ordinary ‘course when 
evagination from the brain took place and has developed to an eve 
in an abnormal place. In my opinion the first supposition is impossible. 
For the changes brought’ about in the head point out that it is 
the eye which chose its course and that the shifted bones and muscles 
adapted themselves to the abnormal condition which they found 
when being formed. If it were the eye that had deviated after the 
bones had developed, not the entopterygoid would have been 
displaced, but the muscle-nerve complex would have grown along 
the bone. Moreover it is not likely that the tongue would have 
been compressed after developing, but that it developed after the 
eye-stalk had formed and so was impeded in its growth. Finally it 
is difficult to understand how with a full-grown eye the cornea 
would have participated in the descent. 
Assuming the second supposition, namely that the eye-vesicle 
already deviated from its normal course when it evaginated from 
the brain, we must, in order clearly to understand the process, 
consider how the condition of the head was when the eye first 
originated. For Muraena Prof. Borkn gives us important data on 
this point. (Die Entwicklung der Muraenoiden, Petrus CAMPER, 
Vol. II, 1903). At the time of the evagination of the eye-vesicles 
also the infundibulum is evaginated ventrally. Before it lies the 
so-called anterior mesodermic mass, a coalescence of mesoderm and 
entoderm, according to Boeke. It consists of a thickened cell-mass, 
proceeding in two wings on both sides of the brain, and of a 
one-layered tongue bordering on the periblast. At a later stage the 
thickened mesodermic mass coalesces with the ectoderm, while the 
lower tongue curves round and coalesces with the intestinal 
epithelium. 
The ectoderm invaginates and grows towards the entoderm of the 
intestine; afterwards the buccal cavity is formed in it. 
The two lateral mesoderm streaks of the head originally form a 
solid mass ventrally of the evaginating eye-vesicles. Later in these 
