138 MALL. [Vov. XIX. 
number as pregnancy proceeds, for it is likely that changes 
which arrest the circulation in the embryo, or feetus, will 
soon end in abortion. Therefore it is to be expected that a 
small number of pathological embryos develop into well- 
formed monsters. 
In specimen No. 293 we have, however, conditions which 
might end in a typical spina bifida, for the tissues over the 
spinal cord are infiltrated with embryo’s blood and are being 
destroyed. The epidermis is intact. Had this embryo not been 
aborted the injury in it is sufficient to permit of an irregular 
growth of the cord to form spina bifida occulta. 
In specimens Nos. 201 and 226 the changes in the central 
nervous system are very pronounced, and had they not been 
quite so severe it is easy to imagine their growth, at full term, 
into a cyclops foetus in the first case and into anencephalus in 
the second case. 
Specimen No. 295 has in it changes which, if extended, 
could affect the cerebrum, and I am inclined to the belief that 
most cases of anencephaly begin in these later stages rather 
than in very young ones, for if they did not how could a 
relatively normal base of the skull develop in them? In this 
foetus correlated development has given form to all the bones 
of the skull, and the proportion of those of the base would 
not change very much in case the vault and brain were 
destroyed, as is found in typical anencephalic monsters at 
birth. Questions like these are open to investigation and will 
give us the key by which we may determine at what time in 
development anencephaly begins, or whether the time is 
at all constant. 
