PELAGIC FAUNA 



73 



The ribbon-shaped ctenophore, Venus'' s girdle (Cestum veneris). 



The ctenophores are pellucid, gelatinous animals which swim slowly by 

 means of eight ciliated ribs. All are luminescent. Most of them are sphe- 

 rical or barrel-shaped, but one, Venus's girdle (Cestum veneris), is like 

 a length of ribbon (Fig. above). We saw this on a number of occasions 

 and were fascinated by the elegant creature's graceful movements and 

 gorgeous yellow and purple colours. But as we stood watching it it would 

 burst into a thousand pieces! A few ctenophores are adapted to crawling 

 as well as swimming. Most of these strange creatures occur in the Indo- 

 Malay region. One evening as we lay at anchor near the Philippines, I 

 found a small specimen of Ctenoplana (Fig. p. 74), clear with delicate 

 brown markins^s. It was so full of life that I was able to observe it for 

 a long time under the microscope, watching it assume the most singular 

 shapes. Several times I saw it extend its two long, feathery tentacles from 

 the two tubular projections on top. 



Some of the most beautiful of marine creatures are the siphonophores. 

 They form free-swimming colonies consisting of many different indivi- 

 duals, each with its own function in the colony: swimming-bells, digestive 

 and reproductive members, protective bracts, and tentacles which defend 



