PELAGIC ANIMAL LIFE 



579 



No class of multicellular animals in the ocean is represented by any- Crustacea, 

 thing like such countless forms and individuals as that of the Crustaceans ; 

 in the life of the ocean they play, according to Haeckel, a part corre- 

 sponding to that of the insects in the land fauna. The Entomostraca 

 include the most important groups, first the Copepoda, then the 

 Ostracoda, and the Cladocera. Among the larger Crustacea, the 

 Schizopoda, the Amphipoda, and the Decapoda are also very important, 

 but in abundance and specific variation they can never be compared to 

 the groups of smaller crustaceans. 



The Copepoda, as a rule, attain only a few millimetres in length, and Copepoda. 

 are adapted to feed on the small plants of the oceanic flora in the upper 

 layers of all oceans. It may safely 

 be asserted that they are the chief 

 consumers of these minute plants, 

 and in turn serve as food for 

 larger animals. 



Giesbrecht ^ discusses the geo- 

 graphical distribution of 299 species 

 of Copepoda, and divides the area 

 of their distribution into three 

 regions: (i) a warm region between 

 47° N. and 44° S., (2) a northern 

 region, and (3) a southern region. 

 The warm region comprises all the 

 oceans, the warm - water species 

 throughout the world being more 

 alike than the species of warm and 

 cold regions in the same ocean. 

 Of the 299 species, no less than 

 254 belong exclusively to the 

 warm region ; there are besides 

 a few widespread forms and others 



peculiar to the northern or southern region. About 85 per cent of 

 the species belong to the warm region, 5 per cent to the northern, and 

 2 per cent to the southern region. 



As characteristic of the warm region Giesbrecht mentions the follow- 

 ing genera: Augaptilus, Calocalanus, Copilia, Euchirella, Heviicalanus, 

 Monops, Pleuromina, Pontella, Pontellma, Sapphirma. Peculiar to the 

 northern area are : Acartia bifilosa, Calanus hyperboretis, C. cristatus, 

 Centropages Jiamatus, EuchcEta norvegica, Pseudocalanus elongatus, and 

 perhaps Teviora longicornis. Some forms are common to the warm 

 region and one of the cold regions, such as Anomalocera patersoni and 

 Centropages typicus, while Calanus fitimarchiciis and Oithona similis 

 occur in all the three regions. 



The warm and cold water forms differ in structure, the body, legs, 

 and antennae of the warm water forms being generally provided with 

 wonderful feather or fan-shaped attachments, which greatly enlarge the 



Fig. 416. 

 Calanus Jinmarchicus, Gunner. 

 After G. O. Sars, from 

 Steuer. ) 



1 Giesbrecht, " Systematik und Faunistik d. pelag. Copepoden," Fauna nnd Flora 

 des Golfes von Neapel, Bd. 19, 1S92. 



