Maturation — eImbryoIiOgucal. Gen. Sub. 51 
Nucleus in ovarian ovum of Triton: The first stage--a coil of chro- 
matin threads— is a palingenetic phenomenon, corresponding to the first 
phase of mitosis. The diffuse threadwork stage which follows is coeno- 
genetic — an exaggeration of the normal nuclear activity. Thirdly, a 
thickening and concentration of the chromatin produces the secondary 
coil, which then enters into mitosis ; Born (51). 
Polar bodies after expulsion: in Amphorina cosrulea , Berghia cosru- 
lescens , &c., the polar bodies remain in contact with the vitellus, touch it 
from time to time, &c. ; Trinciiese (541, 542). 
d. Fertilisation. 
Fertilisation in trout; Blanc (44): in earthworm; Foot (162): of 
mouse ovum ; Sobotta (513). 
Polyspermy in Axolotl ; Gasco (178). 
Fragmentation in unfertilised ovum of rabbit ; Cavazzini (85). 
Plastogamy ; Johnson (261). 
General ; Debierre (114). 
7. Embryolooical. 
Comparative embryology — a text-book ; Roule (461). 
Analytic theory of organic development : The ovum is a mixture of 
potentialities; these are realised in the successive steps of development, 
which are induced by stimuli, and determined by mutual relations of parts. 
Changes are induced partly by internal factors (e.g., tension, pressure, 
&c.), partly by external factors (e.g., gravity). Each period is the con- 
dition of its successor. Each blastomere has the power of responding to 
certain developmental stimuli ; Driesch (127). 
Criticism of Driesch’s theory of development ; Haacke (206). 
Epigenesis or evolution ; Bourne (55), Mivart (364), Hertwig 
(235). 
Hertwig’s preformation or new formation ; Mitchell (361). 
Recapitulation theory ; Marshall (332). 
Embryos of fowl and dog-fish are not closely similar in the young 
stages. Fowl and duck embryos can be distinguished on the second day. 
Embryos of Peripatus capensis and P. balfouri are very different. 
Ancestral stages of structure are only retained in so far as they are use- 
ful to the larva in its free development. Embryonic development, in so 
far as it is a record at all, is a record of structural features of previous 
larval stages; Sedgwick (502). 
Inadequacy of cellular theory of development ; Sedgwick (503), 
Whitman (572a). 
Physiological Morphology : Organs may grow out of their proper 
place, e.g., in excised and inverted parts of hydroids (heteromorphosis). 
