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. Curynea, consisting of the genera Sertularia, Tubu- 

 laria and Coryne ; and 3. Millepora^ limiting probably this de- 

 nomination to M. triivcata. 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 Madrejjores 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 Escharidae, 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. Joiirii. of Geogr. and Nat. Science, ii. p. 406, and Blainv. Man. 



d'Aetinol. p. 59. 



3 



