CHAPTER YII. 



THE CTENOPHORA.l 



CLASS CTENOPHORA. 



Sub-Class 1. Tentaculata. 



Order 1. Cydippidea. 



,, 2. Lobata. 



,, 3. Cestoidea. 



„ 4. Platyctenea. 



Sub-Class 2. Nuda. 

 Order 5. Beroidea. 



Under the name Ctenophora is comprised a small assemblage of 

 organisms, pelagic in habit, characterised by a well-marked biradial 

 symmetry, the possession of rows of swimming plates formed of 

 modified cilia, and a transparent gelatinoid body. The majority 

 of authors classify the Ctenophora as an aberrant group of the 

 Coelentera, the architecture of the body being compared with 

 that of a Hydromedusa ; on the other hand, several authors have 

 claimed affinities between the Ctenophora and Turbellarian worms. 

 It will be most convenient to describe the structure and develop- 

 ment of a typical form of the group, and to discuss its phylogeny 

 afterwards. 



Though the Ctenophora are universally distributed and are 

 especially abundant in warm seas, they were not recognised until 

 1671, and then they were observed, not in warm or temperate 

 seas, but in the neighbourhood of Spitzbergen by a ship's surgeon 

 named Friedrich Martens. Nearly a century later, in 1756, they 

 were again discovered at Jamaica by Patrick Brown, and two 

 species were included in the tenth edition of the Systema Naturae 

 under the names Vohox heroe and Volvox hicaudatus. Since the 

 beginning of the present century Ctenophora have been found 

 and studied in all quarters of the globe. They attracted the 



1 By G. C. Bourue, .ALA. 



