330 



larvae. Thus the larvae of Dalmanites and Proetus, with their prominent 

 eyes, and glabella distinctly terminated and rounded in front, have char- 

 acters which do not appear in the larval stages of ancient genera, but 

 which inay appear in their adult stages. Evidently such modifications 

 have been acquired by the action of the law of earlier inheritance or 

 tachygenesis." 



Bryozoa. — My studies (17, 18) were the first to show that there is in 

 the bryozoan colony a definite recapitulation of ancestral characters, and 

 that in this particular the colony behaves as an individual. This same 

 fact was very clearly pointed out by Ruedemann (47) two years earlier 

 in the Graptolites, and I take pleasure in quoting his very explicit state- 

 ment. He says : "Furthermore the fact that the thecal within the same 

 colony show a gradation from phylogenetically older to younger forms, 

 and therefore analogous to the organ of a growing individual, pass 

 through ancestral stages, as, e. g., do the septa of a cephalopod shell, 

 demonstrates how closely the zooids of this colony were united into one 

 organism, and that practically they were more the organs of an individ- 

 ual than the component of a colony If the graptolites so 



closely approached the morphologic value of an individual, it may be ex- 

 pected that, like an individual, the whole colony has its ontogeny and re- 

 passed ancestral stages." 



My studies, referred to above, brought out the fact that the bryozoan 

 colony begins as a minute hemispherical body, the "protceciuni" which is 

 the earliest exoskeletal stage of the first individual of the colony. This 

 protceciuni (basal disc) is very conspicuous in the Cyclostomata. and also 

 in the ancient Cryptostornata (as shown in Fenestelhi). 1 It can not be 

 definitely asserted that the protoechim corresponds to any ancestral bryo- 

 zoan, but the marked resemblance of the zooeeia of some of the ancient 

 Stomatopora of the Ordovician to the protceciuni is at least very sug- 

 gestive. 



The ancestrula, or first complete individual of the colony, has long 

 been known to present characters more similar to those of ancestral forms 



1 I first used the term protceciuni as the designation of the first individual of 

 the colony, and in this sense it would be exactly equivalent to the term ancestrula 

 of Jullien. In a later paper (18) I restricted the term to the basal disc (of 

 Barrois) which is the calicified wall of the metamorphosed and histolyzed embryo 

 in its earliest sedentary stage. Out of this basal disc the first normal individual 

 arises by a process stirctly analogous to budding. In this sense, therefore, the 

 term protcecium is exactly correlative with the terms protegulum, protoconch, 

 prodissoconch, etc. 



