356 W. G. Van Name — Bermuda Ascidians. 



course to the rectum, which it follows to a point near the atrial 

 orifice. 



The Bermuda species of this genus differ more in the habit and 

 character of the colony than in the structure of the zooids or the 

 form of the spicules. They appear to have the following characters 

 in common : 



The zooids vary in length, according to the species, from less than 

 l mm to 1.6 mm in preserved specimens. The musculature of the man- 

 tle consists of a moderate number (perhaps twenty or more) dis- 

 tinct, though slender, bands running longitudinally. Transverse 

 muscles (with the exception of the sphincters) are but slightly 

 developed in the mantle. 



The transverse vessels of the branchial sac are, however, provided 

 with strong muscles, and each side of the dorsal lamina a strong 

 muscle-band runs longitudinally in the wall of the branchial sac. 

 These two bands, which run ventraily when they reach the posterior 

 end of the thorax, are joined near the posterior end of the endo- 

 style by fibers from different parts of the wall of the thorax, so that 

 they become quite thick, and passing out in a ventral and posterior 

 direction from the upper end of the peduncle, they unite to form 

 the muscle of the muscular process which extends out into the test. 



The tentacles appear to be eight in number, four large and four 

 small ones placed alternately, but I am not certain that there are not 

 more in some cases. The stigmata are long and narrow, about 16 in 

 number on each side in the species with the largest zooids, and some- 

 what fewer in the smaller species. The upper and lower rows of 

 stigmata do not contain quite as many as the middle row. 



The stomach is round or oval and smooth externally, and more or 

 less yellow in color. The gland about the intestine consists of a 

 small number of tubes clasping it. They branch but little, and 

 their terminal portions are not much dilated. 



I have found well developed reproductive organs in only two 

 species [D. savignii and D. porites), but they are probably similar 

 in the others also. The testis, which is single and obtusely conical, 

 is very large, and is situated on the left side of the abdomen, with 

 its base close against the intestine. The vas deferens leaves it at its 

 apex and makes, usually, from eight to a dozen turns about its con- 

 ical surface, like the string wound around a top. It leaves it finally 

 about opposite the stomach.. The ovary is placed between the testis 

 and the stomach. 



