EGG STRINGS IN COPEPODS — HEEGAARD 235 



is partly dependent on the activity of the fish species ; therefore we 

 find the egg strings shaped hke long or short sausages. 



Among the free-living planktonic forms the Cyclops is a clumsy 

 fellow who makes only little speed with his relatively short antennae. 

 The female in her birth pangs, therefore, only jumps around in small 

 spirals and loops without any strong pull on the extruding eggs. The 

 egg masses are drawn out a little before the cement hardens and are 

 shaped into two oval bodies under the abdomen of the female. 



In the Diaptomidae the antennae are long, slender, floating organs, 

 too weak to provide any locomotion for the animal. In this case the 

 thoracopods are the organs for locomotion, sending a propelling cur- 

 rent of water backward. The fourth pair of thoracopods are long 

 and reach nearly to the furca of the telson. Therefore when the eggs 

 are ejected from the oviducts, the thoracopods will send a propelling 

 current backward, circulating the extruding egg masses on the genital 

 segment and producing a single globular egg ball such as is found in 

 most Diaptomidae. In most calanids the cement gland is absent, and 

 the eggs are discharged free in the water. 



In most pelagic Harpacticidae the short antenna and thoracopods 

 propel the animals forward, producing their egg-shaped to sausage- 

 shaped egg strings. Among the sand dwellers of the Harpacticidae, 

 we find small, irregular egg strings, partly shaped by the vacant 

 spaces between the sand grains where the copepods are crawling. 



These are a few examples to show how the shape of the egg strings 

 of the copepods depends not only on the size and number of the eggs, 

 but also on mechanical factors such as the method by which the 

 copepod moves through the water and the speed of this movement. 



LITERATURE 



Claus, C. 



1858. Zur Anatomic und Entwickelungsgeschichte der Copepoden. Arch. 

 Naturg., Berlin, vol. 24, pp. 1-76. 

 Heegaard, p. 



1947. Contribution to the phylogeny of the arthropods: Copepoda. Spol. 

 Zool. Mus. Hauniensis, vol. 8, 227 pp., illus. 

 Rathke, H. 



1843. Beitrage zur Fauna Norwegens. Nov. Act. Acad. Leopold.-Carol., 

 vol. 19, pp. 1-264, illus. 

 Scott, A. 



1901. Lepeophtheirns and Lernaea. Liverpool Alar. Biol. Comm., Mem. 6, 

 54 pp., illus. 

 Wilson, C. B. 



1905. North American parasitic copepods belonging to the family Caligidae. 

 Part L— The Caliginae. Proc. U. S. Nat. Mus., vol. 28, pp. 479-672, 

 illus. 



