72 
CLASSIFICATIONS OF ZOOPHYTES. 
more willingly that they are but modifications, to no material 
extent, of one or other of those which preceded them, are in 
no respect preferable, and evolve no new principle, for surely 
the assumption on Oken’s part that the orders, families, and ge- 
nera in this class, as in the animal kingdom generally, are re- 
gulated by a law which throws them into quaternary sections 
— the number 4 exercising throughout a paramount influence 
— scarcely deserves this praise. It is different with the attempt 
of Rapp, Professor of Anatomy at Tubingen, who in 1829 
published a small work in German on the natural history of the 
Actiniae. He proposed to divide the zoophytes, understanding 
the term in the same restricted sense that I do, into two great or- 
ders, the Exoaria and Endoaria, — the former producing their 
ova or reproductive gemmules from the exterior, while in the latter 
<£ the ova are produced in the interior of the body, and are 
either conveyed outwards by means of oviducts which open by 
separate orifices, or they are discharged by the mouth.” The 
distinction here first pointed out is a very important one, but 
in common with all single characters is of itself insufficient, and 
if rigorously adhered to leads to artificial and unnatural com- 
binations, The Exoaria for example has all its members 
well and distinctly affined, embracing only three families, 1. the 
Hydra ; 2. Corynea , consisting of the genera Sertularia, Tubu- 
laria and Coryne ; and 3. Millepora , limiting probably this de- 
nomination to M. truncata. The Endoaria embraces a wider 
range — the Alcyonea equivalent to the Polypes tubiferes of 
Lamarck ; the Tupipora ; the Corallia including the genera 
Corallium, Gorgonia, Isis and Antipathes ; the Pennatulce ; 
Zoanthes ; and Madrepores with the subdivisions which have 
been introduced by Lamarck. * So far the order labours under 
little error, or is perhaps unexceptionable, but its definition 
would entitle us to place in it also the Escharidse, the Celle- 
pores, and Lymnopolypi, which are all very alien to the families 
which Rapp seems to have had too exclusively under his view. 
The only other classification I shall notice is Blainville’s, — 
the most elaborate of any ; and this author, as it appears to me, 
is the first who allowed the anatomy of the Polypes, abstractedly 
* See Edin. Journ. of Geogr. arid Nat. Science, ii. p. 406, and Blainv. Man. 
d’Actinol. p. 59. 
