374 JV. S. NICKERSON. [Vol. XVII. 



little creatures are extremely sensitive to the condition of the 

 water, and the addition to it of any foreign substance, even in 

 the most minute quantity, is invariably followed by a contraction 

 of the body, which is never succeeded by full expansion. They 

 may readily be killed in an expanded condition, however, by the 

 sudden application of hot fixing reagents. Much of the material 

 I have used for study has been killed in this way by cor- 

 rosive-sublimate solution or by a corrosive-sublimate-formalde- 

 hyde mixture. The best preservation of details of cytological 

 structure is given, however, by the osmic fluids (Hermann's 

 and Flemming's). Only ordinary stains have been used, iron- 

 haematoxylin giving the best results and being the one most 

 employed. 



Summary. , 



1. L, Davenporti is a new species ; the first of the genus to 

 be described from the North American coast. It is character- 

 ized by 1 8 to 29 tentacles ; 2 to 6 buds on each side ; foot orbic- 

 ular, and destitute of foot-gland ; stalk short (about equal in 

 length to body), having a row of large columnar cells along 

 dorsal side and spiral arrangement of muscles to the foot ; pos- 

 session, in many cases, of a pair of flask organs ; presence of 

 mammary organ in females with embryos. 



2. A single large cell, which acts as a sucker, is present on 

 the outer side of the base of each tentacle. 



3. Lateral expansions (alae) are formed by the contraction of 

 the body. 



4. A single row of large glandular (i*) cells occupies the mid- 

 dorsal line of stalk. 



5 . Unicellular glands occur in the foot chiefly about its margin. 



6. Flask organs, which are secretory structures, arise by 

 differentiation of ectoderm cells of a certain region, discharge 

 their contents, and drop off. They are capable of being regen- 

 erated. No similar organs have been described for Endoprocta. 



7. The musculature of the stalk shows a spiral arrangement 

 of fibers in the region of the foot. 



8. Rounded or elliptical bodies containing refractive spher- 

 ules are present in all parts of the parenchyma. These probably 



