J. D. Dana on Zobphytes.. 345 
5. Growing free or attached is a character of minor import- 
ance. It is sometimes a convenient generic distinction, as with 
the F'ungide, but in other cases cannot be appealed to. All spe- 
cies, as is well known, are attached in the young state; and the 
time of becoming free varies with the species, some earlier and 
some later. The Fabella thus pass so gradually to attached 
species, and the animals in the two cases are so completely iden- 
tical, that the separation can be sustained only on the ground of 
convenience in a distribution. We add that in this last men- 
tioned case, the simple species pass as gradually into the com- 
pound, and they are closely connected with the group Huphyl- 
lia, D. (a part of Lobophyllia, Bl., having entire lamella. 
6. Growing massive, or calicularly branched, (aggregate or 
segregate, ) is sometimes a good generic distinction. But polyps 
in contact grow together so readily that it can be of importance 
only when supported by other characters. In the group Mani- 
cina, no line can be drawn between the segregate and coalescing 
species ; and the Cyathophylla are other examples. Difficulties 
in the way of characterizing groups thus arise, which must be 
fairly met and not denied nor overlocked. 
«7. The forms of growth, whether branching, massive or ex- 
planate, afford good distinctions for species, but seldom generic 
characters. We find explanate and massive Gemmipore and 
Porites; explanate, massive, and branching Porites and Manopo- 
re; and erplanale and branching Meruline and Echinopore., 
No more unfortunate generic character can be laid down than one 
drawn from this source: it may, however, be occasionally used, 
when sustained by other characters. The genus Hzplanaria of 
ck is an agglomerate of species of several genera. 
We have elsewhere shown that the sizes of branches, the fre- 
quency of branching, and the width of intervals in groups be- 
tween branches, are good trivial characters within certain limits. 
But in all cases in instituting species, the specimens examined 
should be good and full grown, and not fragments. 
8. Growth by budding from an apical polyp, or from. serial 
budding, are points that may afford good generic distinctions... 
IV. Tentacles and General Character of the Exterior —In 
aeration. » As the whole body takes part in this function, the size 
the Astree, one species was observed by the writer, in which the 
Place of tentacles was supplied by numerous spine-like processes 
Srconp Srrizs, Vol. III, No. 9.—May, 1047. 44 
