530 MR, A. W. WATERS ON 



the very earliest stage has not been seen. The wall of the 

 sac is formed of short cells and at one part touches the embryo. 

 The embryo in early stages (fig. 5) is surrounded by large and 

 long cells, and in some cases is filled up by formative tissue. In 

 later stages, when the embryo is nearly ready for a free existence 

 the large cells of the calotte are readily followed (fig. 6). 



Text-fig. 82. 



Lateral surface of Adeonella platalea. X 25. 



"When the ovicellular sac lias grown to a moderate size thei'e 

 may be, near to the opercular wall, an ordinary polypide, but 

 often there is only a very small one looking like a simple bud, 

 being sometimes not more than a straight tube. There are strong 

 muscles at the distal end on one side for contracting the walls of 

 the ovicellular sac, to which they are attached, as well as to the 

 distal wall. The ovicells of A. polystomella Rss., are smaller than 

 those of the other species, but there is the same thick- walled 

 ovicellular sac. Also, in a specimen of Beania viagellanica B., 

 from Chatham Islands, there is a, large embryo in a thick-walled 

 cellular sac nearly filling the zooecium. This I do not find in any 

 of my specimens from Naples, but there is a pair of sac-like 

 bodies near the distal end, and in the Antarctic specimens these 

 bodies are large and were thought to be for the formation of 

 testes, although there are ordinary testes near the distal end in 

 which the spermatozoa can easily be seen. 



It has been supposed that all the large zooecia of the Adeonidae, 

 namely the gonoecia, are merely for embryos, but this is by no 

 means certain, as some may be for the testes, with which some are 

 nearly filled, but the material available does not permit of my 

 saying much on this point. However, it is only in a limited 

 number of species that there are large zooecia, and the same changes 

 may take place in these as in ordinary zooecia ; for as the gonoecia 



