HYDROIDS OF WOODS HOLE. 377 



spring have the distinctive elongated and spirally annulated pedi- 

 cels and large hydrothecae. But specimens taken in summer, so 

 far as my observations have gone, are uniformly and constantly 

 small --only about one fourth that of typical specimens, and 

 have extremely short pedicels, with only one or two annulae, or 

 with none. I was not unaware that Clarke * had referred to certain 

 variations in size, but he made no special reference to it save as 

 an exception. It was only after careful search among colonies 

 of typical specimens that I was able finally to find an occasional 

 specimen of this dwarfed character. I have satisfied myself that 

 it is but another instance of that tendency to seasonal variation 

 which is well known in other cases. It is well, however, that it 



FIG. 5. < 100. 



be emphasized, as well as the further fact that at certain times 

 dwarf features are distinctive and constant. Fig. 5 shows some 

 of these dwarfs enlarged. 



One other feature may be referred to in connection with this 

 phase. Clarke called particular attention to the appearance in 

 certain hydrothecse of this species of a "wide ring, oramented 

 with from ten to fourteen longitudinal markings, which rises for 

 some distance above the rim and on the summit of which there 

 is borne either an operculum or another ring ; in some cases 



1 Trans. Conn. Acad. Sci., Vol. III., p. 66. 



