PROCEEDINGS OF SECTION D. 487 
subsequently give rise to the cerebellum. The front part— 
corresponding to both fore and mid brain—long remains undivided, 
but subsequently a slight dilatation of the median longitudinal 
fissure appears opposite the anterior ends of the optic vesicles ; this 
is the third ventricle, and the small segment of the brain at the sides 
of and in front of it represents the fore-brain. When the rudiment 
of the third ventricle has made its appearance, the hind-brain has 
become plainly marked into cerebellum and medulla oblongata. 
The lens-involution first appears before the brain shows any 
definite signs of division into parts ; it has the form at first of an 
irregularly-shaped plug of cells, which does not lose its connection 
with the surface epiblast till after the fore-brain has become 
differentiated. It grows into a depression of the optic “ vesicle” 
formed to receive it; the “vesicle” long remains a solid structure, 
the wall of the optic cup only presenting a division into two 
layers at a comparatively late period. 
The nasal pits appear after both eye and ear rudiments have 
become well formed ; they appear as depressions in little three- 
cornered masses of cells between the anterior end of the cerebro- 
Spinal nervous axis and the rudimentary eyes. 
The proto-vertebre appear at about the time when the first 
swelling indicating the brain has become apparent. They are 
remarkable for their small size and their number. They are 
formed as a result of the segmentation of two narrow bands of 
mesoblast lying at the sides of the cerebro-spinal axis. 
5.—NOTES ON THE MUSCULAR FIBRES OF 
PERIPATUS. 
By Wittram A. Haswett, M.A., D.Sc., Professor of Biology, 
University of Sydney. 
In Hatchett-Jackson’s revised edition of Rolleston’s “Forms of 
Animal Life,” there is the following statement with reference to 
Peripatus capensis (p. 320) :— The muscles, with the exception 
of those attached to the jaws, are unstriped.” I have been 
unable to find in any of the original papers* on Peripatus the 
statement that the muscles attached to the jaws are striped, and 
I do not know on what authority Hatchett-Jackson rests in 
making the statement. Owing, however, to the peculiar interest 
which the subjects presents from the point of view of the evolution 
of striated muscle, I made a very careful examination of the 
muscular fibres of the New South Wales species of Peripatus 
* I refer to the well-known papers on the subject by Mosely, Balfour and others. It is 
possible that there may be some statement of this kind in Sanger's paper, which I am unable 
to read. 
