140 Transactions of the Canadian Institute. [vol. ix 



pouches. From the outer side it has the appearance of a double row of 

 rounded lobes. Testicular lobes scattered along upper and lower mar- 

 gins of each ovary; usually on the right side the lobes are above anteriorly 

 and below posteriorly, whereas on the left they are more variable, the 

 majority being below. From i to 4 vasa deferentia on each side (usually 

 2) opening not far from the centre of the inner side of the ovary; the free 

 part of each vas deferens is extremely short and can be seen only with 

 difficulty. 



Specimens obtained at the roots of eel-grass have very short siphons 

 and seemed to fit Verrill's description of Molgiila manhattensis better 

 than that of M. papulosa. In internal anatomy they agree with speci- 

 mens obtained beneath stones at low tide and in the dredgings, which 

 correspond with the description of the latter species. Some of these 

 specimens have siphons as long as those figured by Verrill for Eugyra 

 pilularis. Specimens of M. manhattensis from Connecticut and Rhode 

 Island, kindly sent me by Dr. Van Name, are distinctly different from 

 all northern individuals. They have, as Dr. Van Name stated to the 

 writer in a letter, a narrow dorsal lamina with smooth margin. Other 

 differences are — a smaller, more rounded dorsal tubercle; the testicular 

 lobes are not scattered but massed, being confined to the lower side of 

 the ovary and the inner side of its anterior tip (on the left side, seen from 

 without, the testicular mass appears to curl around the anterior end of 

 the ovary, as figured in 1847 by Van Beneden for his Ascidia ampul- 

 loides, a related species) ; and the free portions of the vasa deferentia 

 are much longer than in C. papulosa. 



The nearest allies of the latter are Molgula simplex Aid. & Hanc. 

 and M. siphonata Alder of the coasts of England. In both of these the 

 testes are in the form of one or two large masses, confined to the inner side 

 of the ovary. It is interesting to note that the English forms are short- 

 and long-siphoned respectively, corresponding with the extreme indi- 

 viduals of the series of specimens of C. papulosa taken at St. Andrews. 



This appears to be the Caesira that is most abundant and most 

 generally distributed near St. Andrews. 



C. canadensis sp. n. 



This is the North American representative of the group to which 

 Lacaze-Duthiers gave the name Ctenicella. 



Body nearly spherical or flattened against the object of attachment. 

 Attached usually by the right side. Up to about i cm. in diameter. 

 Apertures fringed, each oral lobe with 3 teeth, each atrial with from 6 to 

 8. Exposed surface always more or less dirty. Along the margin of 

 the attached area are numerous irregular radicoid filaments. If the 



