No. 7.] OSLER — FRESH-WATER I'OLYZOA. 405 



protrudes, while at the other end it is in communication with the 

 parent polyzoon. Tiie branches are generally attached along 

 the greater part of their length, though sometimes, as in this 

 specimen of P. aretJmsa, they are free in nearly the whole 

 extent. The color is owing to the ectocyst which when first 

 secreted is thin and jelly like but soon becomes consistent, and at 

 last dark brown. The endocyst lies immediately within this 

 and is continuous throughout the system of branches. 



The species of this genus arc widely distributed throughout 

 Canada in the quiet ponds and marshes attached to twigs, sub- 

 mero-ed loirs and the under surface of the leaves of the water- 

 lily. 



The Cristatellida3, the most highly organized of the Polyzoa, 

 have a locomotive ccenoecium. There are two American species 

 C. Idse and C ophidioidea. The one which I have studied here 

 conforms to the latter, as described by Hyatt, in both statoblasts 

 and number of tentacles. It is not nearly so common as the other 

 forms. I have on several occasions met with the statoblasts in 

 gatherings, but have never found the polyp except in the small 

 lakes near the summer residence of Mr. G. W. Stephens, in the 

 County of Maskinonge, Quebec. In Lac liouge, the rocks at 

 water's edge, at about the depth of from one to two feet presented 

 numerous specimens about an inch and a half to two inches in 

 len2;th and one-third of an inch in breadth. The movement was 

 slow, in those which t observed in a small basin, not more than an 

 inch in the 24 hours. The statoblasts diifer from those of Pec- 

 tinatella in possessing a double row of booklets with from two to 

 six points. 



Note. — I have received from the Ilex. Thomas Hincks, the dis- 

 tinguished authority on British Polyzoa, a reprint from the Annals 

 and Magazine of Natural History for March, 1880, entitled "On a 

 supposed Pterobranchiate Polyzoon from Canada."' It is based on a 

 communication from his father, the late Professor Hincks, of Toronto 

 University, in which a short account is given of a polyzoon found on 

 a sunken boat in the Humber river, near Toronto. According to the 

 description "the tentacles, instead of being disposed in a horse-shoe 

 figure and forming a continuous series, as in the ordinar}^ fresh-water 

 species, are borne on two distinct erect lobes, which are separated at 

 the base," the arrangement met with in the Pterobranchiate Polyzooa. 

 At the date of Professor Hincks' letter, Dec. 1868, I was a student in 

 his Natural History classes, and during the autumn of '68 had often 



