GLOSSARY 195 



Sperm (atozoon) : male germ cell. 



Spong^ioplasm: the more solid, fibrous part of the protoplasm. 



Stomodaeum : mouth cavity formed by the ectoderm. 



Syncj'tiiim: multi-nuclear mass of protoplasm. 



Synliarion: zygote nucleus, arising from the fusion of a male and 



a female pronucleus. 

 Teloblast: end-cell of a row of cells. 

 Testis: male reproductive gland. Cf. ovary. 

 Tetraster: mitotic spindle with four poles. 

 Topogenesis: the development of the form of the body through the 



shifting of material during development. 

 Transplantation: grafting of an organ or cell group into another 



place. Cf. explantation, implantation. 

 Triploid: containing three sets of chromosomes. Cf. diploid, haploid. 

 Trochophore: larval stage, occurring in worms, etc., with crowns 



of long cilia by means of which it moves. 

 Trophic: pertaining to the nutrition. 



Ultracentrif uge : centrifuge working at very high speeds. 

 Vacuole: cavity in the cytoplasm, filled with a liquid. 

 Vegetative pole: one of the poles of the egg. Opp.: animal pole. 

 Vegetative reproduction: asexual reproduction. 

 Vitalism: theory according to which the phenomena of life cannot 



be described entirely in terms of the laws of physics and 



chemistry. 

 Vitamins: essential food substances, very small quantities of which 



are sufficient. 

 Vitro, in — : "in glass", term applied to the culturing of tissues 



outside the body. 

 X-chromosome : sex chromosome, playing a role in the inheritance 



of sex. 

 Xenoplastic transplantation: transplantation into an individual of 



another, very distant, species. Cf. heteroplastic transplantation. 

 Zygote: fertilised egg, cell formed by the fusion of two gametes. 

 Zygote nucleus: the nucleus formed by the fusion of the male and 



female pronuclei. 



