PART IV ON O1KOPLEURA TORTUGENSIS, A NEW APPEN- 



D1CULARIAN FROM THE TORTUGAS, FLORIDA, WITH 



NOTES ON ITS EMBRYOLOGY. 



BY WILLIAM KEITH BROOKS AND CARL KELLNER. 



(Plates 3-8.) 

 INTRODUCTORY. 



A large appendicularian (plate 3, fig. 4) in its house is found in abundance 

 in the vicinity of the Marine Biological Laboratory of the Carnegie Institu- 

 tion of Washington at Tortugas, Florida. It is, no doubt, widely distributed 

 along the coast of Florida, as it has been found by Dr. Mayer and Pro- 

 fessor Brooks at Miami, and by Mr. Kellner in the Tortugas. The speci- 

 mens are from 5 to 8 mm. long, and occur in great swarms at the depth 

 of from 5 to 8 fathoms. They belong to the genus Oikoplcnra and to a 

 species that seems to be new, although its differences from O. longicauda 

 and 0. intermedia of Lohmann are slight. The house (plate 3, figs. 4 and 

 5) is large, about 20 mm. in diameter, and nearly spherical. In its internal 

 structure it resembles the houses that have been described in other species 

 of the genus. 



Most of the houses contain small appendicularias of various sizes, 

 but all are well advanced and in the appendicularia-stage. It is possible 

 that these are the young of the animal in whose house they are found, 

 but it is also possible that they have been drawn into the house by the 

 current of water and that they are not, of necessity, the young of the 

 species which forms the house. 



On the tails of some of the specimens (plate 7, fig. 13 ) are the eggs and 

 early stages in the development of an appendicularian which may be Oiko- 

 pleura, although it is possible that they belong to some other species. The 

 eggs (plate 7, fig. 16) are inclosed in thick capsules of follicle-cells. Some 

 are loosely attached to the tails, while others (plate 7, fig. 19) have, at one 

 end, a process of modified follicle-cells that penetrates the tail like a root 

 and firmly attaches the egg. Two embryos, at two successive stages of 

 early development (plate 7, figs. 20 and 15) were found. They are deeply 

 rooted in the tail by a process that penetrates the blood-sinus of the 

 adult, and the embryos are parasites. On the ventral surface of the older 

 embryo (plate 7, fig. 14) the two spiracles, opening to the exterior at 

 one end and into the respiratory pouches of the pharynx at the other, 

 prove that the embryos are appendicularians, although we have not been 



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