596 . NEW YORK STATE MUSEUM 



quite likely that a suspended bell of this kind would have been voluntarily 

 sought by numerous small animals as shelter, as some contrivances of preying 

 water plants are sought by small crustaceans. 



While, however, the specimens of D. flabelliforme from Schaghti- 

 coke are provided with thin, long nemas, Matthew has figured [1892, pi. 49] 

 two representatives of that species with short, broad rootlets. There are then 

 three possibilities : 



1 The presence of the nema in the Schaghticoke specimens and that of 

 the short, rootlike disks in the St John specimens may constitute specific oi* 

 varietal differences, indicative of an entirely different mode of existence. This 

 seems to us very improbable, as it is not supported by any other differences 

 observable. 



2 The thin disk, observed in some young stages at the end of the nema, 

 may grow out into the stouter disk or bundle of rootlets. 



3 The adhesive disk of mature specimens may be a new formation, suc- 

 ceeding normally that of the nema. 



In case 2 it is difficult to understand how the disk at the end of the 

 nema could have wandered along the long nema to the proximal end of the 

 sicula; we believe, therefore« that the disk or root of mature forms was a 

 structure developed toward the mature age of the colony. This inference 

 seems also to be supported by Wiman's observation, that in Discograptus 

 schmidti, another dendroid, the bases of the branches grow directly out of 

 this disk or are embedded in it, that hence it did not form till after the first 

 bifurcation had taken place; and that in D. caver no sum apparently it 

 incloses the sicula. Moreover, we have observed and will demonstrate in this 

 paper that the " central disk " of the Dichograptidae, which is expanded 

 between the branches, is a secondary formation, independent of the primary 

 disk from which the nema of the sicula was suspended. It is proper to 

 conclude that we have in the Dictyonemas a case entirely homologous to that 

 observed in the Dichograptidae. 



Lapworth appears to have made similar observations, for he states 

 [loc. cit. p. 25 3] that certain forms of Dictyonema have a short stem, othei's a 



