1579 
suleus, the caudal part therefore of the s: interparietalis, is found 
back on the bottom of the ape-fissure. This aspect in a brain of a 
macacus, totally agrees with that, which KonLBruGGe (le) reproduces 
in fig. 1, plate V of a semnopithecus maurus. 
The figures 4 to 10 give us a view of the way-in which the 
ape-fissure is developed. 
When the different stages are combined to a whole, the following 
ensues: 
In the embryonal life of the semnopithecus maurus, the principal 
fissures in the first place are formed on the surface of the pallium. 
After that there are two possibilities. Either the lobus occipitalis 
grows further in the same tempo as the lobus parietalis, in which 
case no ape-fissure is formed (fig. 3) or the development of the 
occipital part takes a quicker tempo’), and then the ape-fissure 
indeed is formed. 
In this case one sees in first instance (fig. 6) that the hind lip 
of the suleus parieto-oce. lat. protrudes over the frontlip. If the 
extent of the occipital part still angments, then this posterior part, 
finding no way-out, will grow over the parietal part, lying in front 
of it, pressing this downwards. 
The bridging convolution between the parietal and occipital part, 
being between them, is bent down. (fig. 7). If the process develops 
further, then this bridging convolution will be pushed still more 
into the depth while the s. par. oee. lat. (m—+ m’) is still found on 
the surface (fig. 8). If the occipital part becomes larger, then conse- 
quently, also the preceding parietal part will be pushed downwards 
in the furrow it makes. In this case the m + in’ suleus and a part 
of the w sulcus (the incisure), will no longer remain on the 
surface, but will be found on the frontal lip of the ape-tissure, which 
has been formed (fig. 9). The examination of adult monkey-brains 
has gtaught that the development of the ape-fissure in this period 
can come to a stop, in which case one speaks of an imcomplete 
ape-fissure, because still a part of the bridging convolution (near 2) 
is found on the surface (fig. 1 and 9). If the occipital pole enlarges 
still more, then the preceding parietal part will be pushed still more 
downwards and the entire arcus par. occ. disappears. In this last 
case one finds therefore the incisura par. occ. as well as the sulci 
interparietalis (/-++ e) and par. occ. lat. (m + m’) in the frontal lip 
of the ape-fissure (fig. 10 on the left). One speaks in that ease of 
a complete ape-fissure (fig. 2 and 10). 
Is the meaning right, that the ape-fissure develops through the 
1) This possibility has already been suggested by KoHLBRUGGE on p. 243. 
