366 
CRESSWELL SHEARER. 
ten double chromosomes go out and ten remain iu the egg, 
the ten chromosomes remaining in the egg giving rise to the 
o no o o 
full number again in the first segmentation division. 
(11) In the first and second segmentation divisions of the 
male and female egg twenty chromosomes are present. 
(12) In D. gyrociliatus the presence of large eggs, 
which invariably give rise to females, seems to be due to 
fertilisation, the unfertilised eggs being smaller and giving 
o o o o c 
origin to the males. 
Literature. 
1. Bambeke, Charles Y an. — “ Contributions a histoire de la constitu- 
tion de l’oeuf. Reckerclies sur l’oocyte de Pliolcus,” 4 Arch, 
d. Biol.,’ vol. xv, p. 511, 1898. 
2. de Beauchamp, Paul. — “ Sur l’existence et les conditions de la 
partlienogenese chez Dinophilus,” * Compt. Rend. d. Acad. 
Sci.,’ vol. cl, p. 739, 1910. 
3. Conklin, E. G. — “Sex Differentiation in Dinophilus,’’ 4 Science,’ 
vol. xxiv, p. 294, 1906. 
4. Eisen, G. — “ The Spermatogenesis of Batraclioseps,” 4 Journ. 
Morph.,’ vol. xvii, p. 1, 1900. 
5. Hallez, P. — 4 Contributions a l’histoire naturelle des Turbellaries,’ 
Lille, 1879. 
6. Korsclielt, E. — “ Ueber Bau und Entwicklung des Dinophilus 
apatris,” * Zeit. f. wissen. Zool.,’ vol. xxxvii, p. 315, 1882. 
7. 44 Die Gattung Dinophilus und der bei ihr auftretende 
Geschlechtsdimorphismus,’ 4 Zool. Jakrb.,’ vol. ii, p. 955, 1887. 
8. Malsen, Hans Freiherr von. — “ Geschlectsbestimmende Einfliisse 
und Eibildung bei Dinophilus apatris,” ‘Archiv. f. mik. 
Anat.,’ vol. lxix, p. 63, 1906. 
9. Meyer, Ed. — 44 Studien ueber den Korperbau der Anneliden,” 
* Mitth. a. d. Zool. Stat. Neapel.,’ vol. vii, 1886-7 (pi. xxvii, 
figs. 9 and 10). 
10. Nelson, James A. — “The Early Development of Dinophilus,” 
* Proc. Acad. Nat. Sci. Phil.,’ p. 687, 1904. 
“The Morphology of Dinophilus conklinii,” ‘Proc. 
Acad. Nat. Sci. Phil.,” p. 82, 1907. 
11 . 
