870 THE AMERICAN NATURALIST. [VoL. XXXII. 
diameter. Of these self-regulations Driesch distinguished two 
categories — primary, involving only normal ontogenetic proc- 
esses, and secondary, involving ontogenetic processes of a new 
and special sort. 
Teratology. — The most important work of the year in com- 
parative teratology was that of Patten on abnormalities in the 
development of Limulus, In attempting to produce monstrosi- 
ties by physical agents, Bataillon made the axis of the embryo 
frog lie perpendicular to that of the first cleavage plane 
(hence perpendicular to its normal position) by pressure, Rossi 
found that electricity has less effect the older the embryo, the 
fact that the different chemical solutions have specific effects 
on echinoid ontogeny was determined for echinoids by Herbst 
and for Amphibia by Gurwitsch, Samassa ascertained that pure 
oxygen has little effect on the development of the frog, and Féré 
found that the venom of the viper provokes anomalies in the 
development of the chick. De Vries showed that a highly 
nutritive culture-medium tends to accentuate the monstrous 
characters of individuals of a race of plants which is tending to 
revert to the normal type. Several unusual and well-worked- 
out cases of abnormalities in invertebrates were described by 
morphologists. 
Regeneration. — While the multiplication of cases of regen- 
eration continued as in former years, the principal lines of 
advance in 1896 were first in the clearer recognition of the 
fact that in regenération an organ often arises from dissimilar 
germ-layers and develops in a different manner than it does 
in egg development ; and, secondly, that regeneration is often 
accompanied by heteromorphosis. In the first category we 
have Wolff’s case of regeneration of the lens from the mesoderm 
of the iris of Amphibia, this year abundantly confirmed. Accord- 
ing to both Michel and Hepke, the ectoderm of the earthworm 
gives rise to all the regenerating tissues. In the second cate- 
gory of cases we place the observations that regenerating eyes 
of shrimps may produce antenniform organs, that the vegene 
ating antennæ of the lobster have a spiral form, that planarians, 
whose margins have been incised, may form multiple heads, and 
that the regenerated tails of lizards are of simpler organization 
