yo. 2063. NORTH AMERICAN PARASITIC C0PEP0D8— WILSON. 591 



ONTOGENY. 



The complete life history of Achtheres amhlopUtis has aheady been 

 published.* 



Fasten has also given us an account ^ of the free s^\dmming larva 

 of Sahnincola edwardsii. Some of these copepodid larvae, admirably 

 mounted, wpre loaned to the present author for study and comparison, 

 and have proved of great value. 



It only remains, therefore, to restate the hfe history rery briefly 

 and to compare the larvae of the two genera above named with those 

 of Clavella, the material for which is here presented for the first time. 

 Inside the ovary are many long filaments, which are connected with 

 the older oocytes and whose terminal ceUs develop successively one 

 after the other. In Clavella uncinata (fig. 10) these filaments are 

 given off dorsaUy and pass down ventrally into the convolutions of 

 the oviduct, where the end cells 

 can be seen in various stages of 



development. These filaments ■'' "-^- 



are longer and less convoluted in 



Clavella and Clavellisa (fig. 11) ,. - -J) 



than in Achtheres or Naohranchia ' ' ..j 



(fig. 12). They stain readily and 

 in double-stained sections always 

 show a dark purple color. A vi- F'«- io-e«« filament and developing egg 



^ . .-, -, , IN Clavella uncinata. 



telHne membrane is visible around 



the end cell, even before it separates from the filament. Inside 

 of thismembrane the entire substance of the egg is made up of yolk 

 globules evenly distributed through a fine matrix of protoplasm. Scat- 

 tered about are numerous large vacuoles of different sizes, those nearest 

 the periphery being usually the smallest. As the eggs pass down 

 the oviduct they are each fertilized at the opening of the sperm tube, 

 and are covered with a layer of the cement substance before they 

 pass out into the external sacks. In the latter they segment, and the 

 larvae develop through the nauplius and metanauplius stages before 

 hatching. Segmentation is entirely superficial, the cytoplasm sepa- 

 rating from the yolk, migrating to the surface and there fomiing 

 blastoderm cells around nuclear centers. The yolk remaining inside 

 the egg and afterwards inside the embryo serves to nourish the latter 

 not only through the nauplius and metanauplius stages but also 

 through the free swimming copepodid stage. Since neither the nau- 

 pUus nor the metanaupHus can escape from the egg, their unfolding is 

 necessarily condensed. Usually the three naupHus appendages de- 

 velop and serve their temporal y function before the other appendages 



1 Proc. U. S. Nat. Mus., vol. 39, p. 189. 



2 Report of the Commissioners of Fisheries of Wisconsin, 1911-12, p. 11. 



