314 
found in most genera, namely, the smootli and the spinous ones 
are also represented in this genus. Hartlaub names five species, 
in which tlie gonothecae are smootli while spinous gonotliecae have 
only been found in S. quadrata Nutt., S. tur gida (Trask) and S. 
tamar isca. 
As the large plurality of the Sertularella- species are provided 
with a s talk-mark, there can be no doubt that they have developed 
from stalked forms, and as the hydrothecae in the genus Thyro- 
scyphus are provided botli with a stalk and with a Sertularella- 
operculum, it is permissible to suppose that a large number of these 
an cest ral forms have been short-stalked Thyroscyphus-syecies. 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. Neitber 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. lata (Bale), S. dis - 
tans Allm., S. 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' formosa Fewkes 
and “ Sertularella * Hartlaubi Nutt. In “ Sintegritheca , the only 
one of the three species, which I have been able to examine, the 
diaphragma has a somewhat similar structure as in “S .” 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 
