BOLINA. 



31 



Fig. 31. 



Bolina. (Bolina alata AG.) 



THE Bolina (Fig 32), like the Pleurobrachia, is slightly oval in 

 form, with a longitudinal split at one end of the body, forming a 

 mouth which opens into a capacious sac or digestive cavity. 

 But it differs from the Pleurobrachia in having the oral end of 

 the body split into two larger lobes (Fig. 31), hanging down 

 from the mouth. These lobes may gape 

 widely, or they may close completely 

 over the mouth so as to hide it from 

 view, and their different aspects under 

 various degrees of expansion or contrac- 

 tion account for the discrepancies in the 

 description of these animals. We have 

 seen that the Pleurobrachia moves 

 with the mouth upward ; but the Bo- 

 lina, on the contrary, usually carries 

 the mouth downward, though it occasionally reverses its position, 

 and in this attitude, with the lobes spread open, it is exceedingly 

 graceful in form, and looks like a white flower with the crown 

 fully expanded. These broad lobes are balanced on the other 

 sides of the body by four smaller appendages, divided in pairs, 

 two on each side (Fig. 32), called auricles. These so-called 

 auricles are in fact organs of the same kind 

 as the larger lobes, though less developed. 

 The rows of locomotive flappers on the Bo- 

 lina differ in length from each other (Fig. 

 31), instead of being equal, as in the Pleu- 

 robrachia. The four longest ones are op- 

 posite each other on those sides of the body 

 where the larger lobes are developed, the 

 four short ones being in pairs on the sides 

 where the auricles are placed. At first sight 

 they all seem to terminate at the margin of the body, but a closer 



Fig. 31. Bolina seen from the broad side ; o eye-speck, m mouth, r auricles, v digestive cavity, g h 

 short rows of flappers, a f long rows of flappers, n x t z tubes winding in the larger lobes ; about half 

 natural size. (Agassiz.) 



Fig. 32. Bolina seen from the narrow side ; c h short rows of flappers, ab long rows of flappers ; 

 other letters as in Fig. 31. (Ayassiz.') 



