f)9Q NEW YORK STATE MUSEiUM 



more the organs of an individual than the component of a 

 colony. Colonies are morphologically composite, but act physi- 

 ologically as a unit. There are however all gradations from 

 loose aggregates of individuals forming colonies to organisms 

 in which, by division of labor, consequent supression of indi- 

 viduality and the presence of common organs, the colony also 

 morphologically approaches closely to the character of a sole 

 individual, e. g. the Siphonophora. Several important features 

 of the graptolite colonies indicate that they also partook to a 

 considerable degree of the character of a morphologic indi- 

 vidual. This is specially suggested by the observation that 

 several of the composite dichograptid colonies, as illustrated 

 by the minute stages of Tetragraptus and Phyllograptus 

 (fig. 18, 19), even in the earliest stages developed, by a 



rapid budding from the ex- 

 tremely small immature the- 

 cae (thecae are here meant 

 Fig. is Tetragraptus Fig. 19 Phyiio- to include or represent the 



bigsbyi Hall. Minute graptus illcifol- ., , . , , , 



growth stages. Sieular ana ius Hall. Very ZOOldS, WHICH are not OD- 



antisicular views. x3J^ young growth stage. 



x3 servable), the fundamental 



lines of the mature structure. This was possible because 

 the buds are produced near the proximal ends of the 

 mother thecae. Only afterward the thecae grew to ma- 

 ture size. This premature inauguration of the process 

 of gemmation in individuals which have attained only a 

 small fraction of their mature size, while reproduction in 

 the animal kingdom takes place normally only in adult speci- 

 mens, and the subsequent expansion of the whole stage, demon- 

 strate that the early stages of these colonies did not grow by 

 mere addition of buds, but also as entities. In the latter 

 process, however, the thecae (zooids) appear entirely devoid of 

 individuality and only as the subordinate parts of a whole grow- 

 ing body, which is then, certainly, to be regarded as a morpho- 

 logic individual in so far as it grows as a unit or individual. 

 The same uniform growth of the whole young colony took place 

 also in Goniograptus, as the comparisons of the dimensions of 



