436 PROCEEDINGS OF THE NATIONAL MUSEUM. tol. 45. 



primary. Dorsal tubercle small, the hypophysis mouth a simple, 

 narrow horseshoe in shape. Brancliial sac with six folds on each side, 

 none of the folds with less than 6 longitudinal vessels, and some "with 

 12 or 13, never more than one vessel between the folds, more fre- 

 quently none at all, the individual vessels on the folds broad and strong 

 and usually close together; transverse vessels very few, entirely 

 absent for long stretches in the spaces between the folds; infundibula 

 reaching deep into the prominent folds, but not easily seen on surface 

 views of the inside of the sac on account of the crowded condition of 

 the longitucUnal vessels of the folds; stigmata long, rather regular, 

 and usually straight and directed lengthwise in the spaces between 

 the folds. Dorsal lamina "^vith plain edge throughout its course. 



Alimentary system. — The narrow intestinal loop situated on the left 

 side, but far back and extending across the entire body; the two 

 limbs of the loop almost in contact with each other except at the closed 

 end, this end again bent sharply forward making a short second double- 

 tubed loop. Stomach but Httle greater in diameter than the gut; 

 the wall presenting a number of low, rather inconspicuous irregular 

 lobes. Anus situated very close to the atrial orifice, the rim nearly 

 or quite plain. Renal organ an elongate, bean-shaped body situated 

 far back on the right side, somewhat concave on its anterior edge and 

 convex on its posterior edge to correspond with the rounded outUne 

 of the body, length nearly equaling one-half the longest diameter 

 of the body removed from the test. 



Reproductive system. — Voluminous on both sides of the body, that 

 of the left lying above and close along the intestinal loop ; that of the 

 right above and close along the renal organ, reacliing down somewhat 

 on the anterior end of the latter. Ovary and testes mtimately com- 

 mingled, the cyhndric ovary occupying the middle and entirely sur- 

 rounded by the testes; the mass of the left side as long as tne intestinal 

 loop and in addition extending into and quite filling the concavity 

 of the secondary loop. 



So far as I am able to determine tiiis species has more in common 

 with M. impura Heller, 1887, than any other species. From this it 

 differs, however, in having a harder test, in possessing a maximum of a 

 dozen or more longitudinal vessels on the largest branchial folds, and 

 in the limited size of the gonad of the right side. According to 

 Michaelsen, 1908, who had made a careful study of HeUer's species, 

 the right gonad extends around the anterior half of the renal organ. 

 "VVliile in our species the testis part especially reaches well dowTi across 

 the anterior end of the organ, it does not pass around on to the pos- 

 terior side. 



Hartmeyer, 1912, has made a commendable effort to mark off a 

 number of subgroups Avithin the genus Molgula. The leading pomt 

 made use of by him m this classification is the number of longitudinal 



