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found in most genera, namely, the smooth and the spinous ones 
are also represented in this genus. Hartlaub names five species, 
in which the gonothecae are smooth while spinous gonothecae have 
only been found in S. quadrata Nutt., S. turgida (Trask) and $. 
tamarisea. 
As the large plurality of the Sertularella-species are provided 
with a stalk-mark, there can be no doubt that they have developed 
from stalked forms, and as the hydrothecae in the genus Thyro- 
scyphus are provided both with a stalk and with a Sertularella- 
operculum, it is permissible to suppose that a large number of these 
ancestral forms have been short-stalked 7%yroscyphus-species. I 
have found the gonothecae of Th. ramosus Allm. and Th. Torresi 
Busk, in which two species they are indistinctly ringed, and there- 
fore they present no difficulty to such a supposition. Neither does 
the diaphragma, which is developed as a marginal thickening in the 
whole circumference of the hydrotheca and, therefore, corresponds 
to the thickened marginal portion of the diaphragma found in most 
Sertularella-species. But such species as S. Zata (Bale), $. dis- 
tans Allm., $. magna Nutt. and S. flabellum (Allm.), in which 
the diaphragma is either quite absent or only represented by a 
narrow adcauline belt cannot have developed from Thyroscyphus, 
and the same, no doubt, holds good also for the earlier mentioned 
group of species, the cylindrical hydrothecae of which are free in 
their whole length, but quite lack a stalk-mark. To Sertularella 
have also been referred a small number of species provided with 
free cylindrical hydrothecae, but without an operculum, namely 
""Sertularella” integritheca Allm., "Sertularella” formøsa Fewkes 
and " Sertularella” Hartlaubi Nutt. In "$.” integritheca, the ons 
one of the three species, which I have been able to examine, the 
diaphragma has a somewhat similar structure as in "8." cylindri- 
theca, and I am inclined to think, that the same is the case, with 
the two other species. I cannot refer the three species to Sertul- 
arella as they lack the chief character of this genus, but it is 
possible that the cylindritheca group may have developed from the 
