I04 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



The method of formation of the stalk is clearly only 

 another illustration of the phenomenon of polymorphism 

 so frequently met with among the Bryozoa. The stalk 

 of Ascorhiza consists of transformed zocEcia as unmis- 

 takably as do the ovicells of Crisia or -the avicularia of 

 Biigula. The evidence for the homology of zooecia and 

 muscle plates lies first in their similar origin. Each arises 

 as a small bud within the gelatinous matrix, and in the 

 transitional region represented in fig. 3, the one cannot be 

 distinguished from the other in the earliest stages. Farther 

 evidence is afforded by the cross-section (fig. 5), in which 

 the mode of growth of both muscle plates and zooecia is 

 shown to be similar in the adult stage, that is, in the older 

 parts of the stalk there is a certain amount of overlapping 

 just as there is in the zooecia of the capitulum or of the 

 base. Furthermore, the green body represented in fig. 4, 

 g. b., is extremely suggestive of the histolyzed remains of a 

 polypide, such as are found in the capitulum. The muscle 

 plates are regarded, then, as highly differentiated zooecia, 

 whose polypide bud has been transformed into muscle 

 fibres. They form distinct muscular elements of the Asco- 

 rhizan colony, and may be termed myoecia, whose function 

 it is to elevate the colony and to afford it a means of 

 movement. 



Although the stalked condition shown in Ascorhiza is a 

 unique feature in the family Alcyonidiidae, yet an approxi- 

 mation to it is found among some of the erect Alcyonidia. 

 If the lower portion of the ordinary Alcyonidium gelati- 

 nosuni be examined, it will be found to be more or less 

 modified. In a small cylindrical colony about four inches 

 high and half an inch in diameter, the lower zocecia for the 

 distance of an inch from the base have become somewhat 

 changed, or rather, somewhat less gelatinous, and may be 

 regarded as supporting structures. 



During the course of the Fur Seal Investigations in 

 Alaska in 1896-97, under the direction of Dr. David Starr 

 Jordan, several specimens of Bryozoa were collected at the 

 Pribilof Islands which show an approach to the stalked 

 condition of Ascorhiza. They resemble pedunculated 



