526 NEW YORK STATE MUSEUM 



conspicuous bilateral symmetry, as Wiman has pointed out [1893, p.269] 

 This author lays great emphasis on this fact in the discussion of the possible 

 relations of the graptolites to the Hydroidea, and we shall recur to this 

 character in a later chapter [p. 576]. 



Lap worth, as early as 1876, when describing two species of the new 

 genus Dimorphograptus, expressed his belief that the sicula never develops 

 more than one bud, even in the diprionidian forms. This view has been 

 confirmed by Holm's, Wiman's and the. writer's observations on represen- 

 tatives of different orders of the graptolites, and it can now be asserted that 

 in all graptolites but one bud originates from the sicula. 



With this the process of continuous budding is initiated, which results 

 in the formation of the rhabdosomes. 



Series of growth stages of colonies have thus far been published only by 

 the present writer, viz those of the synrhabdosomes of Diplograptus 

 foliaceous [1895] and of the rhabdosomes of Goniograptus thu- 

 reaui [1902, p.576-93], to which is added in this publication a series of 

 the growth stages ofDictyonema flabelliforme. It thus happens 

 that these represent the three orders of graptolites, the last named graptolite 

 giving an example of the development of the Dendroidea, Goniograptus 

 thureaui of the axonolipous Graptoloidea, and Diplograptus foli- 

 aceus of the axonophorous Graptoloidea. 



The astogenetic series^ of Dictyonema flabelliforme is described 

 in greater detail under that species. We shal], therefore, mention here but 

 the principal facts. It begins with a distinct sicula, provided with a very 

 long nema and a primary disk [pl.l, fig-l]- From the sicula buds first a 



^ We adopt here a recent suggestion by Dr E. R. Cumings [Development of Some 

 Paleozoic Bryozoa. Am. Jour, Sci. 1904. 17:50], who submits a new set of terms for 

 the growth stages of a colony in distinction to those introduced by Hyatt for the ages of 

 an individual, and shall use here the term astogenetic series for these growth stages of a 

 colony. In a former paper [1902, p.591], in which for the first time has been pointed 

 out the recognition of stages in the development of a colony which correspond to the 

 ontogenetic growth stages of an individual, we have employed the terms of the latter 

 series in a wider sense. 



