72 Gen. Sub . 
I. , GENERAL SUBJECTS. 
modifies directive-divisions and cleavage ; §ala (615). — Action of gases, 
&c., on eggs of insects ; Perroncito & Bosso (522).— Experimental 
studies of the blastula and gastrula stages of Echinus ; Morgan (478). 
— Influence of yolk on gastrulation and the formation of the germinal 
layers ; Samassa (617, 6}8).— Grafting Amphibians : when a tadpole is cut 
into two, the pieces may unite if kept close. Two tail ends may unite 
and live for eight days. The anterior part of one larva may be united to 
the posterior part of another. Two may be united by ventral surfaces. 
Larvae of different genera may be united ; Born (57). — Influence of cold 
on development of hen’s eggs ; Kaestner ( 333). — Development of de- 
nucleated Echinoderm ova ; Boveri (62). — Fertilisation of non-nucleated 
fragments. Shaking ova induces development in larva of characters 
belonging to another form; Morgan (479). — Experiments on teratogeny; 
F6 r6 (190). — Influence of electricity on developing embryo of fowl ; 
Dareste (137). — Action of various substances on the developing egg of 
the hen ; Friati (191). — Influence of injection of nicotin on the develop- 
ment of fowl’s egg; Fer6 (192). — The experimental study of meroblastic 
Vertebrate eggs possible ; Mitsukuri (455). 
Epigenesis aut Evolutio . 
Evolution and epigenesis ; Whitman (752). — Palingenesis ; Whitman 
(754). — Problems and methods of developmental mechanics; Roux (596a). 
Epigenesis and Evolution : — Epigenesis, argued for. The disposal of 
cell-material is determined in the course of developmental processes 
according to the various conditions and relations ; Hertwig (303). — 
Theory of epigenetic development ; the three-fold rhythmic harmony 
in ontogeny ; Garbowski (230). — Evolution or epigenesis ; Hiller 
(310). — Theory of development. Preformation in the germ has no 
foundation in fact. Corpuscular evolutionist theories mistake effects for 
causes ; thus “ ids,” “ idants,” &c., “ are produced as passing shadows, so 
to speak, in the operation of the perfectly continuous processes of meta- 
bolism incident to development.” The germ-cell is a dynamic system, a 
unity, not isotropic, but aeolotropic, whose molecular mechanism deter- 
mines initial steps which determine others. Throughout, of course, 
external forces sustain the moving equilibrium. The germ is an auto- 
matic mechanism in virtue of its molecular structure and its store of 
potential energy. Each step in its development is dynamically, metaboli- 
cally, conditioned by its antecedents, and conditions within limits what 
follows ; Ryder (602). — Theory of development. Criticism of Hertwig’s 
“ Neo-epigenetismus.” Each step in development is the necessary result 
of the specific organisation of the germ-plasm. In early cleavages there 
is unequal partition of the hereditary qualities. External conditions are 
simply stimuli, not directly operative factors ; they allow the nature of 
the Anlage to assert itself ; Nusbaum (494). — Hertwig's theory of 
development ; Wagner (723). — External stimuli in development ; von 
