SOME OBSERVATIONS ON ACINETARIA. $39 
flattened in a direction at right angles to that in which the 
attachment of the proboscis lies, and it is probable that the 
proboscis arises from the surface which is ventral in the 
ciliate embryo. The base of the animal is directly attached 
to the supporting hydroid, as may be readily seen in longi- 
tudinal sections, 
128 jb 
TEXT-FIGURE 1 a.—Part of a longitudinal section of a Pro- 
bosecidiform individual of Ophryodendron abietinum, 
to show the origin of the proboscis. 
1 b.—Part of a longitudinal section of the distal portion of 
aproboscis to show the relations of the tentacles to the pro- 
boscis. 
Ma. Macronucleus. My. Myonemata. Ne. Nematocysts. 
Te. Tentacles. W. Wall of proboscis. 
The proboscis takes its origin rather low down on one 
surface of the animal (text-fig. la), and passes forward 
between two lateral thickenings which I shall term the 
apical lobes. It is from these apical lobes that the vermiform 
buds take their origin. During life the proboscis is in con- 
stant motion, expanding and contracting rapidly. In an 
ordinary Proboscidian individual the proboscis in the con- 
tracted condition measures about 66 u, but when fully expanded 
