~42 FOURTH REPORT — 1834. 



primary division is grounded on the position of the ovaries or 

 germs, which are either external or internal, and give rise to two 

 groups accordingly. The former includes the genera Hydra, 

 Coryne, Sertularia, and Tuhularia, united to form a small 

 family ; and the genus 3Iillepora. The latter comprises the 

 Alcyonia, or Polypi tubiferi of Lamarck ; the TubiporcB ; the 

 Corals ( Corallium, Gorgonia, Isis, and Antipathes) ; the Pen- 

 tiatulfs ; the genera Zoanthus and Cornularia ; and the Ma- 

 drepores. The second part of Rapp's work is confined to the 

 ActiniiB, and may he regarded as a kind of monograph on that 

 difficult tribe, the species of which have been in general so ill- 

 determined. 



The same year as that in which Rapp published the above 

 work, he also published a paper, in the fourteenth volume of the 

 Nov. Act. 3)'c., Nat. Cur., on the structure of some species of 

 Polypi from the Mediterranean. 



It is not pretended, in what has gone before, to point out all 

 the discoveries which have been made in this class of late years ; 

 and possibly there may be some of more importance than any 

 mentioned which I have omitted, through ignorance, to notice. 

 But whatever our knowledge may amount to, we may safely say 

 that it bears but a small proportion to what remains to be ac- 

 quired. This is indeed true with respect to every department of 

 zoologj^, but it is most especially so with regard to the present. 

 As a proof, it is only necessary to mention that in Blainville's 

 work (I speak of tlie second edition, which appeared during the 

 present year,) there are upwards of fifty genera (without includ- 

 ing those which have been hitherto only found fossil) the cha- 

 racters of which commence vf'iXh animaux inconmis* . I need 

 scarcely add what a field is here open to the naturalist, or how 

 far we must be removed from imderstanding the structure and 

 the true natural affinities of all the above groups. 



5. Infusoria. — So complete a revolution has been effected in 

 this group by the recent brilliant discoveries of Professor Ehren- 

 berg, as entirely to sink the value of every arrangement that 

 had been previously brought forward of the animals which it in- 

 cludes. It is not, however, a department of zoology which had 

 before been much cultivated. Since the time of Miiller, to 

 whom we are indebted for the first accurate researches into the 

 history of these minute beings, but little progress has been made 

 in our knowledge respecting them, till the period we are about 

 to speak of. The most important contributions were those of 



* One of these geneva is Antipalhes, the animals of which, however, have 

 heen discovered h)' Mr. Gray, who read a short notice respecting them to the 

 Zoological Society in 1832. See Proceed, of Zool. Soc. for that year, p. 41. 



