254 W. HAROLD LEIGH-SHARPE 
The characteristic spiral can be well observed in an ordinary 
film preparation made as follows: Spread upon a slide a thin 
smear of the fluid exuding from the urogenital aperture. Al- 
mm, 
Fig. 3 Seyllium ecanicula, a transverse section through the abdominal region 
of an animal one day after hatching (borax-carmine). F.R., fin ray; m., myo- 
meres; N.C., nerve cord; V.C., cartilage of the vertebra; L.V., lateral vein; 
N., notochord and its sheath; D.A., dorsal aorta; M., kidney (mesonephros) ; 
M.D., mesonephric (Wolffian) ducts; M.R., mesonephric (Wolffian) ridge; P.C.V., 
posterior cardinal vein; L., liver; C., coelom; Int., intestine; J.A., iliac artery; 
S., siphon. 
low nearly to dry, but not quite, breathing on the surface to 
keep moist those peripheral parts which exhibit a tendency to 
desiccation. 
