12 MALL. [Vot. XIX. 
again received its death-blow from J. F. Meckel, who pointed 
out the well known fact that many structural anomalies are 
hereditary. This observation naturally divided terata into 
two groups: those which are hereditary and germinal, and 
those which are not hereditary but due to mechanical injury 
or disease. I think this line of division should be drawn 
much sharper than it is, but until our data can be arranged 
better than is now possible we are still quite uncertain re- 
garding a large number of terata. It seems to me that many 
merosomatous terata (all kinds of anatomical anomalies and 
variations of the extremities, like polydactyly and possibly 
some cases of arrested development like ectrodactyly and 
hare-lip) are germinal and cannot be produced experi- 
mentally. Other monsters in which more or less of the 
foetus is destroyed, as in iniencephaly, spina bifida, anen- 
cephaly, cyclopia, club-foot and many varieties of arrested de- 
velopment, are not germinal but are produced in some me- 
chanical way which usually interferes with the nutrition of 
the embryo. In my notes I have been in the habit of calling 
those belonging to the first group as being abnormal and 
those to the second group as pathological. The one is 
germinal with a hereditary tendency, and the other is acquired 
and therefore not hereditary; polydactyly is inherited, cyclo- 
pia is not, although there seems to be a tendency for it to 
occur more than once in abortions from the same woman. 
However, if this is true, it may be due to the same cause in the 
uterus of the mother affecting the nutrition of successive ova, 
thus producing similar deformities in the embryos. Usually 
a woman who gives birth to several monsters has the varie- 
ties mixed up pretty well, the first may have hydrocephalus, 
the next hare-lip and the third cyclopia. Reducing it to a 
matter of chance, a woman who has given birth to one 
monster is more likely to give birth to a second one, which, 
however, is rarely like the first. In experimental teratology 
in birds and amphibia the result is the same. Here monsters 
may be produced experimentally with a variety of agents, 
even by treating the semen of toads with X-rays, but the 
