144 



INDEX AND GLOSSARY 



Frogs' eggs, Hertwig's experi- 

 ments upon ; development of, 

 under compression, 57-60. 



Funaria, reproduction from 

 chopped pieces, 46. 



G. 



Galls, 50. 



Gastrula, an early embryonic 

 stage, most simply formed 

 from the blastosphere by the 

 invagination of one side of 

 the wall, and consisting of 

 a hollow sac, the walls of 

 which are formed by two 

 layers of cells, xviii, 60 ; for- 

 mation of, 99. 



Gernmules. See Pangenesis. 



Germ, the youngest embryonic 

 stage of an individual or 

 organ, 10. 



Germplasm, the substance sup- 

 posed to be the material 

 bearer of inherited qualities : 

 Weismann's conception of, 

 viii, 20; identification of, 

 with nuclear matter, 21 ; 

 account of Weissmann's 

 theory, 21-28. 



Germ-tracks, the hypothetical 

 paths along which germ- 

 plasm passes in an un- 

 altered condition during 

 development, 27 ; objections 

 to, 81. 



GOBBEL, on plasticity of plants, 

 120. 



Grafting, 68, 70 ; of Hydra, 72 ; 

 bone -grafting, 73, 74 ; skin- 

 grafting, 74, 120, 121. 



GRASSI, polymorphism due to 

 food, 129. 



Gregarines, a group of parasitic 

 protozoa, development of, 

 41. 



H. 



HAACKE, declaration that Hert- 

 wig is evolutionary, 135. 



Haemoglobin, the red colour- 

 ing matter of blood, 75. 



Harmonic union in grafting, 

 70. 



Heteromorphosis, explanation 

 of, 49 ; cases of, 51, 52 ; 

 embryonic cases, 54. 



His, presence of foci in the 

 germ, 13. 



Histogenous, producing micro- 

 scopical characters, 20. 



Histology, study of the micro- 

 scopical characters of cells 

 and tissues, differentiation, 

 115. 



Hydatina, determination of 

 sex, 5 ; temperature, 123. 



Hydra, regeneration in, 47 ; 

 grafting of, 72. 



HydroniedusEe, a group of in- 

 vertebrate animals, the 

 typical members of which 

 are branched colonies of 

 polyps : Weismann's in- 

 vestigations on, viii, xii. 



Hypoblast. See Epiblast, xvi. 



Hypotrichous infusoria, a group 

 of protozoa, 41. 



Ids, hypothetical individual 

 pieces, a number of which 

 are supposed by Weismann to 

 be present in the germplasrn 

 of every sexual cefi, and each 

 of which is supposed to con- 

 tain the inherited material 

 necessary for a complete new 

 organism. It has been sug- 

 gested that tiny beads seen 

 within the chromosomes of 



