*» 



1905.] NATURAL SCIENCES OF PHILADELPHIA. 377 



considered as established. Nevertheless, so far as budding worms are 

 concerned, no distinctions can be detected, unless the number of setae 

 averages somewhat less in American specimens. The prostomium is 

 often slightly pigmented, but there are no eyes. The blood is pale 

 greenish-yellow, and the chlorogogue cells pale brown. The first bud- 

 ding zone usually occurs at XX or between XIX and XX. A second 

 may occur at XXXV, but usually only the first is conspicuously devel- 

 oped. Still attached zooids may possess as many as 28 or 30 segments 

 before the appearance of a second budding zone. In buds nearly ready 

 to become detached both dorsal and ventral setse occur on all segments. 

 All through July and August active budding continues under natural 

 conditions, but worms kept throughout the autumn at Philadelphia 

 failed to develop genital organs. 



Nothing but its small size and mode of occurrence has caused this 

 species to be overlooked for so many years as it is extremely abundant 

 and widely distributed. More than any other species it withstands a 

 wide range of density in the water, being almost equally at home in the 

 rain-soaked eel-grass above high tide, on the shores of brackish ponds 

 and under stones near low-water mark on the exposed shores of Vine- 

 yard Sound, Its movements are characterized by frequent quick, 

 nervous turnings and contractions. 



Clitellio arenarius (Mailer) Savigny. 



Lumbricus arenarius Miiller, 1776. 

 Clitellio arenarius SaAigny, 1820. 

 iLumhriculus tenuis Leidy, 1855. 

 Clitellio irrorata Verrill (in part), 1873. 



Of the ten species noticed in this paper the present one is the largest, 

 full-grown examples exceeding two inches in length and a millimeter in 

 diameter at the clitellum. Preserved specimens usually have the 

 mouths of the spermathecse and the penes protruding in the form of 

 prominent papillae, as Prof. Verrill has noted in his description. Sex- 

 ually mature worms are abundant, enabling one to secure cocoons in 

 numbers and to study the anatomy of the genital organs with ease. 

 There is little doubt of the identity of the American and European 

 worms, the only noticeable differences being a slightly greater average 

 number of setae in ours and an apparently somewhat shorter sperma- 

 thecal duct than is figm-ed by European authors. No entirely satis- 

 factory figures of the setae of the Eiu-opean worm have been found, and 

 it is possible that there may be a difference in their form also. The 

 spermathecae are often filled with large vermiform spermatophores. 



The distribution of this form is equally extensive on the European 

 and American sides of the Atlantic. It is excessively abundant in 



