No. 2.] SOME BERING SEA TUNICA TES. 'JC) 



The facts which I here present relating to reproduction 

 pertain to Synoicum ^ alone. They are, in outline, as follows : 



On examination the colonies are found to contain zooids in 

 various stages of degeneration, as well as those in a normal 

 condition. Some of these degenerating individuals are with- 

 out the thorax ; others, again, are lacking both thorax and 

 intestinal loop, the post-abdomen alone being present, this lat- 

 ter, however, retaining quite its normal form and structure. 

 In still other zooids the post-abdomen, which alone remains, 

 is reduced from its original club shape to a spherical form. 



The post-abdomen, as with all the polyclinidae, lodges the 

 heart, the epicardiac tubes, the sexual organs, and a variable 

 quantity of mesenchymatous tissue, the cells of which contain 

 a characteristic granular material which apparently is food 

 yolk. This last-mentioned substance constitutes, in this 

 species, by far the major portion of the bulk of the post- 

 abdomen at the time when the latter becomes free from the 

 rest of the zooid. 



The ova at this time appear to be all contained in the 

 compact band-shaped ovary, and are in many stages of growth. 

 They are all, excepting the very largest, almost entirely free 

 of yolk ; they possess neither recognizable follicular epithe- 

 lium nor " test " cells, and they are distinctly amoeboid in form. 

 Careful examination of the ova discovers that many of them, 

 particularly the larger ones, contain within the substance of 

 the cytoplasm other cells in various stages of disintegration. 

 They are ingesting other cells ; they are clearly amoeboid in 

 habit as well as in form. 



Beside the amoeboid ova contained in the ovary there occur, 

 in some of the post-abdomens that have become more nearly 

 spherical in form, ova in which the amoeboid character is 

 wholly wanting, they being quite spherical in form and regu- 

 lar in outline. In these ova, which are also considerably larger 

 than the largest amoeboid ovarian ova, the cytoplasm is no 



1 Synoicum is a compound ascidian in which the colony is composed of a 

 number of lobes arising from a common basal mass. Each of these lobes con- 

 sists of a groundwork, or matrix, of firm, homogeneous testicular substance, in 

 •which are imbedded a small number of zooids. 



