REPORT OF THE STATE PALEONTOLOGIST 1901 



587 



Fig. 14 Goniograptus thureauivar. 

 postremus. a branch ; b proximal thecae 

 enlarged ; c distal thecae enlarged. 



while the later thecae h, widen more rapidly, lie more diver- 

 gent from the axis of the branch (their outer margin forms an 

 angle of 28° with the axis), overlap more than one half, have 

 concave apertures and a slightly 

 projecting outer apertural margin. 

 7 It becomes apparent from 

 these observations that the thecae 

 of the colony of Goniograptus, 

 from the sicula through the stolo- 

 nal and early brachial thecae to 

 the distal brachial thecae, form an 

 ontogenetic series, which furnishes 

 a clear and interesting example of 

 " localized stages of development ", the existence of which has 

 been demonstrated and their character elucidated by R. T. Jack- 

 son.^ In this remarkable publication it is stated (p. 90) : 



In organisms that grow by a serial repetition of parts, it is 

 found that there is often an ontogenesis of such parts, which 

 is more or less clearly parallel to the ontogenesis of the organ- 

 ism as a whole.- In the ontogeny of such localized parts in a 

 mature individual, we find stages in the development during 

 the growth of the said part which repeat the characters seen in 

 a similar part in the young individual. To state it briefly for 

 the moment, such localized stages have been observed in the 

 leaves of plants, in branches or suckers of plants, in the bud- 

 ding of some lower animals, as Hydra and Galaxea, in the plates 

 of crinoids and Echini, in external ornamentation in mollusks, 

 and in the septa of cephalopods. 



From the examples cited those of Hydra and Galaxea are the 

 most pertinent to our inquiry. In regard to them Prof. Jackson 

 makes the following note (p. 141): 



In animals which produce asexually by budding, as Hydrozoa 

 and Actinozoa, it seems that the bud may be considered a local- 

 ized stage. The bud has not the stages seen in early embryonic 

 development from the egg, but repeats in general the later 

 stages- seen in such ontogeny. A bud is not a new individual 

 in the full sense of the word, but is an outgrowth from an older 

 individual by a special localized development. 



^ Bost. soc. nat. hist. Mem. 1899. v. 5, no. 4. 



