1 82 CALIFORNIA ACADEMY OF SCIENCES. [PROC. 3D Ser. 



of the embryozooid. Furthermore, as the colony grows, 

 the size of the ampullse increases, until in the large adult 

 colonies they are very much larger than in the embryo- 

 zooids. (Compare text-figures i and 2, both magnified 43 

 diameters.) 



Pizon (1900, pp. 48, 49) is undecided whether to seek 

 the decrease in the ampullae and the shortening of their 

 pedicels in the mechanical retraction of the ampullae due to 

 the decrease in the size of the zooid to which they are 

 attached, or in an actual degeneration of the proximal part 

 of the pedicel, similar to the resorptive processes going on 

 in the degenerating zooid. He is, however, certain that 

 this reduction in size is not momentaneous, such as would be 

 produced by a contraction of the cells of the ampullar wall — 

 a conclusion entirely in accord with that of the writer. 

 Concerning the real cause of this decrease, however, it will 

 be seen from the text (p. 141) that the writer considers it to 

 be a resorption of some of the nutritive substances or living 

 protoplasm of the cells of the ampullge and their pedicels; 

 and not to either mechanical retraction of the ampullae or to 

 a bodily disintegration and degeneration of any of its 

 constituent cells. 



The evidence which has led to this conclusion, and which 

 is not mentioned in the text, is as follows: The tips of the 

 ampullae, unlike the rest of these organs, are normally 

 composed of a rather high cylindrical epithelium. At the 

 time when the ampullae are retracted from the edge of 

 the test and decrease in size, this columnar epithelium 

 becomes much lower, and in many cases, where the colonies 

 were kept in aquaria, was seen to disappear altogether, the 

 tips of the ampullae being composed of a flat epithelium, 

 similar to that making up the rest of the wall of the ampullae 

 and vessels. Here, then, in the case of these columnar 

 cells we can see some process of resorption taking place, 

 and the conclusion seems justified, that the decrease in the 

 size of the whole ampullae and its pedicel is due to a similar 

 but less evident resorptive process taking place in all of the 

 cells of the organ. 



