256 
side find the same form of inflorescence in different classes, ordines 
etc., and at the other side different inflorescences in the same 
family or even genus. In the Bryozoa we find the same unstable 
relation between structure and colonial form, and a great number 
of species may even appear in two or more different modes of 
grovvth, and with different arrangement of the zooecia. The most 
interesting example we possess is Membranipora (Electra) pilosah. 
which according to A. M. Norman 1 ) appears in the Trondhjem 
Fjord in 10 different modes of growth, a number of which were 
earlier regarded as the chief character of certain genera. The 
author savs about these forms: “We see enormous changes brought 
about apparently at the will of individuals, who, building colonies 
after the various fashions characteristic of a large number of 
genera. simulate the general forms of a Membranipora, a 
Ilippothoa , a Carbasea, a Flustra , a Cellaria , a Gemellaria and 
an Eucratea. Numerous other examples are named in my work 
on the Cheilostomatous Bryozoa 2 ). 
As to the Hydroids there is no reason to believe that the 
arrangement of the zooids should in this division be a more true 
expression of the natural affinity than in the Bryozoa. I shall at 
this place only bring forward as an example the artificial genus 
Selaginopsis (Allman) Mereschkowsky, as Schneider 3 ) regards it 
as one of the best defined genera in the family Sertulariidae. 
Nu tt in g 4 ) has given a new definition of it, according to which 
it only contains species of the genera Thujaria and Sertularia, 
but he does not raention where he will put the polyserial species 
of the genus Diphasia. According to the original definition of 
*) 43, p. . 
2 ) 35, p. 70. 
3 ) „Deutlicli sich aus diesem Chaos abhebend standen nur Pasythea ... 
und Hydrallmania . Auch Selaginopsis Allman kann wegen 
vielreihiger Anordnung der Hydrotheken an der einzelnen Sympodien 
nicht zweifelhaft gestellt erscheinen, obgleich Levin sen sie auf drei 
seiner Gattungen, Sertularia , Thujaria und Diphasia auftheilt (54, 
p. 521). 
*) 44, p. 127. 
