280 PROCEEDINGS OF THE AMERICAN ACADEMY 



body-wall by their cuboid form. They finally give rise to lateral 

 branches, in which polypides are secondarily developed. 



Braem has ofPered the ingenious hypothesis that the tip of the branch 

 is to be regarded as having been occupied, ancestrally, by a polypide 

 which has coenogenetically disappeared. Young polypides are on this 

 assumption derived from the neck of older ones, as in Phylactolae- 

 mata. This hypothesis is rendered less necessary, if one conceives 

 that in the budding process the younger bud is not derived from the 

 older, but that they are successively derived from the same mass of em- 

 bryonic tissue, — a view which I have already maintained concerning 

 Phylactolajmata. The tip of the branch is, to my mind, to be regarded 

 as a stolon in both the median and lateral branches. To form the 

 polypide, the two layers of the embryonic mass of the wall are, in Pa- 

 ludicella, invaginated into the coelom. But some of the cells remain 

 in their indifferent condition as the neck of the polypide. 



As Braem saw in the living animal, and as my sections and recon- 

 structions sufficiently demonstrate, the hinder part of the alimentary 

 tract arises in a manner comparable with that in Phylactoloemata, and 

 its formation progresses from the anal towards the oral end. The 

 oesophagus arises independently, and later the two pockets fuse to 

 form the completed alimentary tract. The tentacles arise somewhat 

 differently from those of Phylactolajmata, and in the manner recently 

 described by Seeliger for Bugula, and they as well as the kanipto- 

 derm are here two-layered. They lie at first in two parallel rows of 

 seven each. The anus is not removed outside the tentacular corona 

 until the two posterior free ends of the ring canal meet and become 

 confluent between mouth and anus. An odd tentacle, younger than 

 the others, often arises directly oralwards of the anus. The brain 

 arises as in Cristatella, and sends out two large circumccsophageal pro- 

 cesses to form the commissure. The so-called epistome of Korotneff, 

 Nitsche, and Seeliger, which they have believed to exist in the early 

 stages of different Gymnolajmata, is merely the fold separating the 

 brain cavity from the oesophagus, and has no relation to the epistome 

 of Phylactoloemata or Endoprocta. I have found no trace of a true epi- 

 stome at any stage. The body-wall is invaginated at the neck of the 

 polypide, and the latter extends as a long cylinder for some distance 

 below the general surfiice. It secretes the chitinous rods and cuticula 

 of the adult " neck." The " collare seto.^ura " appears to split off 

 from the thick cuticula of the neck as a delicate chitinous cylinder, 

 which has its distal end free and its proximal end embedded in the 

 cells of the neck immediately around the atrial opening. From its 



