64 BULLETIN OF THE 
Davenport, ’90, Plate IX. Fig. 77, Plate XI. Fig. 98) and Paludicella 
(Plate V. Figs. 50 and 45). 
As my purpose is not so much to present a complete organogeny of 
3ryozoa as to show the method of origin of the bud and the fate of the 
layers, I have had to desist from carrying on my studies further in the 
organography, and have left many interesting and important questions 
unsolved ; such, for instance, as the development and structure of avi- 
cularia, the presence of an excretory system, and the degenerative pro- 
cesses which occur with regularity in the polypides. 
3, REGENERATION OF THE POLYPIDE. 
I have been led to study the regeneration of the polypide because 
Ostroumoff seems to believe that in regenerating buds the digestive epi- 
thelium of the stomach is derived from an extraneous source, — the 
brown body. Thus he says (’86", p. 340) the brown body appears as a 
ceocal appendage of the young digestive tube. “est sur ce dernier 
[tube digestif] qu’on trouve un groupe de cellules affectant la forme 
d’un bonnet et se réunissant très tôt à Vangle proximal du rudiment 
ectodermique. A mesure que les cellules du bonnet, ainsi que la masse 
brune, sont employées & la formation de la portion moyenne du tube 
digestif, ces dernières se débarrassent de leur contenu,” etc. 
The external phenomena of regeneration are well known. In the 
Membranipora stock, for instance, one sees polypides being produced at 
the margin, and one finds them older and older as one passes backwards, 
until finally they are seen to be wholly degenerate, and to be replaced by 
young polypides. Thus, in passing backward along a single row of indi- 
viduals in a Membranipora stock about 18 mm. long, I have seen this 
process of regeneration recurring four times. In Aleyonidiun, too, one 
finds an apparently regularly recurring degeneration and regeneration 
of polypides. In the mat-like Cheilostomata the regenerating polypide 
(Plate VIII. Fig. 71, pyd. rgn.) is always found at one place, — namely, 
on the operculum, — that is, proximal of the opercular opening.t In 
Flustrella it is found in a similar position on the dorsal body wall, proxi- 
mal of the cuticularized introverted portion. My studies have been 
chiefly made on the Cheilostomata. Figure 91 (Plate X.) represents an 
early stage in the formation of a regenerating polypide. Here, as in the 
marginal polypides, there is a typical invagination involving the two 
1 Haddon (’83, pp. 522, 523) has found the regenerating polypide arising from 
the same place in Flustra membranacea and in Eucratea, and Ostroumoff (786s, 
p 389) in Cheilostomes in general, 
