SEX DETERMINATION IX DJNOPHIbUS GYROCILIATUS. 367 
12. Obst, P. — “ Untersuchungen uber das Yerhalten der Nucleolen bei 
der Eibildung einiger Mollusken und Arachno'iden,’’ * Zeit. f. 
wissen. Zool..’ vol. lxvi, p. 161, 1899. 
13. Rapiaclioff, W. — ' On tlie Anatomy and Embryology of Dino- 
pliilns gyrociliatus,' Odessa, 1886. (In Russian, consulted 
from a translation kindly lent me by Dr. Harmer.) 
14. Schimkewitscli, W. — “ Zur Kenntnis des Banes und der Entwick- 
lung des Dinopliilus vom Weissen Meere,” ‘Zeit. f. wissen. 
Zool.,’ vol. lix, p. 46. 1895. 
15. Schmidt, O. — " Zur Kenntniss der Turbellaria rhabdocoela und 
einige andere Wiirmer des Mittelmeeres,” ‘ Sitzunb. Akad. Wiss. 
Math. Natw. Klasse. Wien,’ vol. xxiii, p. 1, 1857. 
16. Shearer, C. — “On the Anatomy of Histriobdella h omari,” 
* Quart. Journ. Micr. Sci.,’ vol. 55, 1910. 
17. — “The Problem of Sex - determination in Dinopliilus 
gyrociliatus,” ‘Journ. Marine Biol. Assoc.,’ vol. ix. No. 2, 
p. 156, 1911. 
18. Stiasny, G. — “Dinopliilus apatris forma tergestina,” ‘ Zool. 
Anz.,’ vol. xxxv, p. 587, 1910. 
19. Weldon. W. F. R. — ■“ On Dinopliilus gigas,” ‘Quart. Journ. 
Micr. Sci.,’ vol. xxvii, p. 109, 1886. 
20. Whitney, D. D. — “ Observations on the Maturation Stages of the 
Partlienogenetic and Sexual Eggs of Hydatina,” ‘Journ. 
Exp. Zool..' vol. vi, p. 137, 1909. 
EXPLANATION OF PLATES 30-34, 
Illustrating Mr. Cressvveli Shearer’s paper on “ The 
Problem of Sex Determination in Dinopliilus 
gy roc i 1 ia t u s.” 
Lettering. 
an. Anus. cent. Centrosoine. cl. r. Ciliated rings, e. Eye. fe. pro. 
Female pronucleus. <j . Gut. ni. Mouth, m. pro. Male pronucleus. 
mu. yl. Mucus glands, me. ten. Median hairs or tentacles, neph. 
Nephridia. as. Oesophagus, ov. Ova ov. f. Female eggs. ov. m. 
Male eggs. ph. Pharynx, pr. b. Problematic body. pr. b. 1 . First 
polar body. pr. b* Second polar body. sol. Solenoeytes of nephridia. 
si. <J. Salivary gland, spr. Sperm, st. Stomach, tes. Testis. 
