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BULLETIN OE THE UNITED STATES FISH COMMISSION. 
such as evaluations of the column-wall ( Aliciidoe Bunodmoma , 1900a, pp. 13, 28), 
and a strong constricted sphincter muscle (e. g., Stoichactis, Actinoporus , p. 118) 
may appear in any group, and that their occurrence does not necessarily imply 
any relationship in the forms possessing them. Undoubtedly this is in the main 
correct when isolated structures only are considered, but the classifications hitherto 
have been founded more upon a combination of features, and the greater the number 
which can be shown to agree the more likely are the forms to be closely related. 
Just as isolated characteristics may denote no natural relationships between their 
possessors, so certain primary characteristics may be retained by different species 
whose other features show them to be widely separated. It is really a question of 
determining which characters are homoplastic and which are homogenetic. 
By adopting the course proposed by Carlgren it is evident that a duplication of 
groups within the two sections, Protanmem and Nynanthem . must arise. Within the 
Protanthece may be species which have evolved in practically all directions known to 
actinologists, and also in the section in which the ectodermal musculature is lost will 
be forms modified along exactly similar lines. This is at once evident in the necessity 
for the subdivision of the hitherto sharply defined Stic/ioddetylince. Tentacular dis- 
position becomes subordinated to histological details. Though most students would 
probably admit that the old tribe St/icliodaetylince includes polyphyletic groups, yet 
to remove its simplest members seems to render impossible any natural arrangement. 
I am also of opinion that once its importance is fully recognized, the ectodermal 
columnar musculature will be found in forms in which it has hitherto been over- 
looked. Except where maceration of fresh material can be resorted to it will be 
difficult to determine with certainty its presence or absence. Thus in sections of the 
column-wall of Corynactis, Actinotryx , Actinoporus , and Phymanthus , 1 have described 
appearances which would generally be assumed to indicate a weak muscle layer, but 
which, according to Carlgren, may be only the swollen ends of the supporting cells. 
I have not since had the opportunity of proving by means of maceration of fresh 
tissues whether the appearances described are actually referable to the presence of 
muscle fibrils or not, but considering the importance which is now attached to the 
question, and the possibility of the appearances being otherwise explained, 1 have in 
the present paper refrained from further reference to the genera in this connection. 
Until the extent of the occurrence of the columnar ectodermal musculature and 
its association with other features have been more fully ascertained, it seems to me 
hazardous to break up, on its account, long-established systems of classification. 
Where forms have developed along similar lines from some ancestor it is more 
logical that they should be associated than that species should be kept together 
merely because they retain one or more ancestral characters. The combination of 
characters, both primitive and evolved, should be taken into account; the selection 
of only one would give an artificial character to any group. 
1 The family Aliciidx is characterized by a weak musculature and the column possessing simple or complex hollow 
evaginations. The genus Bunodeopsis , in which I first ascertained (1897) the presence of an ectodermal columnar 
musculature, will, according to Carlgren, have to be removed to the Protanthcx along with another representative, 
Thaumactis. In my description of the two species of the genus Bunodeopsis I had not realized the importance which this 
character has now assumed, nor of the other features associated with it, and therefore the account is incomplete in several 
essential details. The columnar ectodermal musculature in Bunodeopsis is strongly developed on delicate mesoglceal 
plaitings, and the nerve layer is also very clearly indicated. The stomodseal ectoderm likewise displays a muscular and 
nervous layer. No gonidial grooves occur and the internal musculature is very weak, the sphincter being of the diffuse 
endodermal type. The parieto-basilar is very feeble, and basilar muscles are absent, but a well-developed tentacular 
sphincter is present. Associated with these, however, are ciliated streaks on trilobed mesenterial filaments. 
Thus the genus agrees in the main with Carlgren’s definition of the tribe Protanthcx. 
