SPERMATOZOA 9 



Its development [v. Belar, 1928 h) shows that the simplest 

 type of spermatozoon in the higher animals {e.g., Stenobothnis) 

 consists of four constituents : (i) Nucleus, making the " head " 

 of the sperm ; it is dense and stains deeply like the mitotic 

 chromosomes. (ii) Centrosome, a cytoplasmic body, lying at the 

 base of the nucleus, forming the " middle-piece " and often divided ; 

 from it develops the axial filament of the "fiagellum" or tail, 

 (iii) Mitochondria, cytoplasmic bodies making the sheath of the 

 axial filament, (iv) Undifferentiated cytoplasm making a thin 

 coat over the head and flagellum — part of the cytoplasm of the 

 parent cell having often been rejected. (C/. Bowen, 1924 ; 

 Schrader, 1929.) 



Sharp (1920, et al.) has shown that the development of the male 

 gamete, the " spermatozoid," in the Pteridophyta follows the 

 same course. It is possible to trace the origin of the spermatozoid 

 from its antecedents : the material of the nucleus and the 

 " blepharoplast," which corresponds to the centrosome and the 

 middle-piece of the animal spermatozoon ; it, also, is concerned 

 with the development of cilia on the coat of the spermatozoid. The 

 cytoplasm from the mother-cell is left behind by the ripe gamete. 

 In the flowering plants it is possible to show genetically and 

 cytologically that in some species plastids are carried into the egg 

 cell by the pollen tube, in others nothing but the nucleus passes 

 from the male parent in fertilisation. 



As a constituent of the male gamete the nucleus alone is constant 

 in its contribution. All functional spermatozoa contain a nucleus 

 which can be traced to one of the four bodies of chromosomes 

 separated at meiosis. In certain organisms such as the flat-worm 

 Ancyracanthus (Mulsow, 1912) and Filaria (Meves, 1915) the 

 chromosomes can be counted as discrete bodies in the live and ripe 

 sperms. The non-nuclear constituents, on the other hand, are 

 variable in the proportion of their contribution. The same is true 

 of the antherozoids of the lower plants. The centrosome, the only 

 other permanent structure constantly carried by the sperm, is 

 actually the one which is lost by the egg and transmitted on the 

 male side only. 



Both sperm and pollen grains are formed on occasion, particularly 



