GAMETOGENESIS AND SPOROGENESIS 



223 



In some animals, notably certain arachnids, crustaceans, myriapods, 

 and nematodes, the spermatozoon has no tail.^^ Although the structures 

 developed in such bizarre types of sperms are very different from those 

 of the ordinary flagellate type, Bo wen finds that they are derived from 

 the same components of the spermatid. For example, the "refringent 

 body" in nematodes, the "capsule" in decapods, and the ''honeycomb" 

 and "valves" in myriapods are all derived from the Golgi apparatus and 

 hence may be compared to the acrosome of other spermatozoa. 



The Structure of Other Ciliated Cells. — In addition to zoospores and 

 gametes, there are other cells which possess special motor 

 structures. Of particular interest are the motor apparatus 

 of flagellates and the ciliary mechanism of certain epithe- 

 lial tissues. 



Many types of motor apparatus are known in motile 

 organisms. 2^ In Menoidium (Fig. 136) the apparatus con- 

 sists of a single flagellum, a blepharoplast, a centrosome 

 at the surface of the nucleus, and a rhizoplast connecting 

 the blepharoplast with the centrosome. At the time of 

 cell-division the blepharoplast divides, its halves remaining 

 connected for a time by a slender paradesmose. Similar 

 in many respects is the mechanism in Peranema (Hall and 

 Powell; Brown). In Polytoma and other forms with two 

 flagella (Fig. 110) there are also two blepharoplasts, be- 

 tween which a paradesmose is usually present, at least dur- 

 ing division.-^ In some instances a centronema is said to 

 extend from the centrosome inward to a karyosome. In 

 Trichomonas niuris there is a single body which acts as 

 both blepharoplast and centrosome. To this " centroblepharoplast " 

 are attached three short, free flagella and one long one forming the margin 

 of the undulating membrane. Along the base of the membrane and 

 connected with the blepharoplast is a "chromatic basal rod," and 

 within the cell may be seen certain other peculiar differentiations. As 

 mitosis begins, the blepharoplast buds off a smaller new one and the 

 two diverge like centrosomes to opposite poles of the achromatic 



2^ See Bowen (19256) and literature there cited; also Sokolow (1929o6). 



^^ For accounts of the flagellar apparatus of flagellates and Protozoa, see Minchin 

 (1912), M. Hartmann (1911), Wilson (1925), Calkins (1926) and the papers by 

 R. G. Sharp (1914), Yocum (1918), C. V. Taylor (1920), Rees (1921), McDonald' 

 (1922), Hall (1923, 1925a), Hall and Powell (1928), Kofoid and Swezy (1915-1923), 

 Kofoid and Christiansen (1915), Entz (1918), Nieschulz (1922), Belaf (1921), Wenrich 

 (1921), A. S. Campbell (1926, 1927), Bunting and Wenrich (1929), Kater (1929), and 

 V. E. Brown (1930). For accounts of cilia and their action, see Heidenhain (1911), 

 Lundeg&rdh (1922), Petersen (1929), Gray (1928, 1931), and Lucas (1932). 



'^''Polytoma uvella (Entz, 1918), Chlamydomonas nasuta (Kater, 1929), Oxyrrhis 

 marina (Hall, 1925a). 



Fig. 136.— 



Menoidium in- 

 curvum, showing 

 motor appara- 

 tus. See text. 

 (After Hall, 

 1923.) 



