84 LEWIS R. GARY. 



viewed from the side, as in this figure, the lines corresponding 

 to the insertion of the old mesenteres are seen to extend only 

 a short distance upward from the base and to be less distinct 

 toward that side which is most nearly perpendicular, i. e., which 

 has arisen from the tissue which was originally part of the pedal 

 disc The tentacle buds have increased very slightly in size,, 

 but at the oral end of the fragment, which now has the appearance 

 of a partly contracted Aiptasla there can be made out through 

 the almost transparent column wall, the outlines of the stomo- 

 deum and the lines of insertion of the developing mesenteries. 



Figs. 4 and 5 were, in order to show the arrangements of the 

 tentacles, drawn in a nearly oral view, so that the upper part of 

 the column is not visible. The fact that the lines of insertion 

 of the old mesenteries appear to extend nearly the whole length 

 of the column is thus to be explained by the foreshortening in 

 the figure and not by any difference as regards the mesenteries 

 between these specimens and that shown in Fig. 3. In the speci- 

 men shown in Fig. 4, there are eight tentacles, of which one is 

 considerably longer than the other seven, all of which are of 

 approximately the same length. In practically all instances one 

 tentacle outstrips the others in its development so that for a 

 considerable time it may be distinguished from the others. On 

 the other hand there seems to be no such definiteness in the de- 

 termination of just what tentacle shall first appear as there is in 

 many actinian embryos where the tentacle above the endoccele 

 between the two dorsal directive mesenteries almost invariably 

 makes its appearance first. 



In later stages there is often a very marked difference in the 

 sizes of the tentacles of the first series, as in the specimen repre 

 sented in Fig. 5. Here a single tentacle has far outstripped the 

 others, while of the remaining seven three are decidedly larger 

 than the remaining four. In Fig. 5 the tentacles of the second 

 set are seen to be arising in pairs at each side of several of those 

 of the first set. While that tentacle of the first set which is 

 uppermost in the figure is by far the longest, there is on either 

 side of it a single short tenacle of the first set, and no indication 

 of the paired tentacles of the second series. The tentacles on 

 the opposite side of the disk have already acquired their definite 

 shape and appearance. 



