90 Papers from the Marine Biological Laboratory at Tortugas. 



able to make out much of their development from two imperfectly preserved 

 specimens of such minute size. The so-called gland-cells that have been 

 figured and described by Lohmann on the tail of Oikopleura are no doubt 

 eggs or embryos. 



All of the houses that we examined contained small elongated gregarina- 

 like parasites (plate 3, fig. 6). On the tails of some of the specimens 

 are rhizopods of the genus Gromia rooted in the tails by a network of 

 pseudopodia, and with the body covered by a thin transparent shell (plate 

 4, fig. 12). This rhizopod is described on page 93. 



Oikopleura tortugensis sp. nov. (Kellner). 



(Plates 3 and 4, figs. I, 2, 3, 4, 5, 8, 9, 10, 11.) 



DIAGNOSIS OF THE SPECIES. 



Both slightly elongated. Dorsal outline convex in profile view (fig. i). 

 Ventral surface between anus, a, and mouth, /, strongly convex. Mouth 

 nearly dorsal. Whole surface of body, dorsal or anterior to a line that 

 joins the anus to the dorsal end of the reproductive organ, covered with 

 large cells (plates 3 and 4, figs. I, 2 and 3). In region of oikoplast there 

 are four membranoplasts, c, c, one on each side of the middle line of 

 the dorsal surface, and one on each side of the body dorsal to the rectum 

 and anterior to the anterior end of stomach. 



Endostyle nearly vertical, anterior end near mouth, posterior end much 

 anterior to the spiracles. 



Digestive organs (plates 5 and 6, figs. 7, 8, 9, 10). Stomach large; 

 with two lobes. The oesophagus opens into left lobe at some distance from 

 its posterior end, which terminates in a dorsal conical protuberance. Right 

 lobe is continued into the intestine, which becomes much enlarged near 

 the anus. 



Reproductive organs (plate 5, figs. 7, 8) convex posteriorly, anteriorly 

 consisting of two concave lateral portions that partially cover the posterior 

 ends of the lobes of the stomach, and a thicker central portion that lies 

 between these lobes. 



Length of body of our largest specimen, 2.5 mm. 



Tail (plate 4, fig. n) broad, with well-developed muscles; end of tail 

 broad, rounded, with no terminal fold. 



House (plate 4, figs. 4 and 5) spherical, delicate, transparent, with two 

 openings, p, p, through which water enters, and an unpaired opening, q, 

 through which it is discharged and through which the animal leaves it when 

 it is abandoned. 



Distribution. Abundant near the Dry Tortugas and in Gulf Stream 

 near Cape Florida. 



Remarks. The differences between this species and O. longicauda and 



