66 Cumings — Development of some Paleozoic Bryozoa. 



fundamental type, which is determined by the position and 

 orientation of the primary buds. It may, therefore, be posi- 

 tively asserted that, ontogenetically considered, the zooscia of 

 Fenestella always lie on the outer surface of the cone. 



It is now necessary to consider the question of the original 

 definition of Fenestella. Several authors have recently 

 restricted this genus to forms having the zocecia on the inner 

 surface of the cone, notwithstanding the fact that Lonsdale, 29 

 in his original diagnosis of the genus, distinctly states that they 

 lie always on the outer surface ! It does not appear to the pres- 

 ent writer that the fact that Lonsdale 20 afterward redefined the 

 genus so as to make it practically coterminous with the whole 

 family of Fenestellidse, as at present accepted, has anything to 

 do with the question. In any subsequent restriction of the 

 genus by other authors, the original sense of the original pub- 

 lisher of the genus should have been ascertained and followed 

 as closely as possible. The first species mentioned by Lons- 

 dale under the newly erected genus is Fenestella Milleri, 

 named after Mr. Miller, who had already proposed the genus 

 in manuscript. F. Milleri clearly and unmistakably has the 

 zooecia on # the outer surface of the cone. There cannot be the 

 slightest doubt that F. Milleri represents Lonsdale's original 

 conception of the genus. In the face of this fact the claims of 

 Gorgonia antiqioa and Fenestella plebeia, which Mr. Shrub- 

 sole 41 identifies with it, must be considered as worthless. 



JEphebastic and Gerontastlc Stages. 



The detailed consideration of adult and senile stages of the 

 zoarium of Fenestella raises certain points the discussion of 

 which the writer prefers to postpone till a more complete sur- 

 vey of the specific representation of this and related genera can 

 be undertaken. Enough has been determined, however, to 

 make it certain that the founding of species upon slight varia- 

 tions occurring on small fragments of zoaria is an exceedingly 

 questionable practice. The modifications of zoaria due to age 

 may be profound. The writer has, for example, seen hundreds 

 of specimens of most exceptionally well-preserved Lower Hel- 

 derberg and Hamilton Bryozoa, in very many cases showing the 

 entire zoarium. These specimens make it perfectly certain that 

 many of the species that have been enumerated from these 

 formations, and founded on fragments of zoaria, are spurious. 

 They may often enough represent merely different growth 

 stages of a single individual. The only reliable criterion of a 

 species is the entire zoarium. 



