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suleus no doubt has to be interpreted as a suleus simialis, yet no 
operculising is found. 
Here we see a sulcus, crossing the lobus occipitalis, which for 
the greater part does not reach. the medial edge, in which no sulei 
end, in which no operculising is found, but which, notwithstanding 
all this, yet should be an ape-fissure. 
This proves most clearly that in ateles, which belong to quite 
another family than the catarrhini, the ape-fissure is represented in 
a totally different manner. 
In Nyeticebus tardigradus again the ape-fissure demonstrates itself 
in another form. 
3RODMANN *), who describes the brain of this monkey, points out, 
that in contrast to others, he found in a specimen which he examined, 
a furrow that could be nothing else but the ape-tissure (pg. 327). 
In this monkey the suleus interparietalis was missing, and the 
ape-fissure appeared as a cross-suleus over the posterior part of the 
brain-surface. In this case there should be an ape-fissure, even 
without the sulei which in the semnopitheci enter into it, and which 
are found there on the brain surface. 
Therefore this case too proves, that the appearance of a sulcus 
simialis is totally independent of whether certain sulci are present or 
not on the brain-surface. 
In short I may say, that although the ape-fissure in certain species 
may be found at the same place, this place in different species can 
change. 
COUN Ca Ursa O UN: 
1. The sulci interparietalis (/ + e) and parieto-occipitalis-lateralis 
(m+ m') appear in foetal life as one sulcus. 
2. The ape-fissure only appears after the other principal fissures 
have been formed. 
3. If a smaller or larger part of the lobus occipitalis develops more 
strongly than the preceding part, through which the latter is pushed 
downwards, then a suleus appears; the ape-fissure or fissura simialis. 
4 The operculum occipitale therefore is primary, the sulcus 
secundary. 
5. If the development of the lobi takes place proportionally, in 
which case the occipital part does not develop quicker than the 
1) BRODMANN, Beitrage zur histologische Lokalisation der Grosshirnrinde. V. 
Journ, f. Prych. u. Neurol. Bd. VI, S. 296. 
