GENUS DACTYLOPORA. 127 



Genus XI — Dactylopora (Plate X). 



187. History. — The most singular varieties of opinion have existed as to the true cha- 

 racter of the fossil organisms on which the genus Dactylopora was founded by Lamarck (lx). 

 They had been previously noticed by Bosc, and had been referred by him to the genus 

 Heteporitcs, belonging to the group then regarded as Zoophytes, but now ranked as Polyzoan 

 Mollusca ; and in this allocation he was followed by Laraouroux. In separating them gene- 

 rically from Betcpora, Lamarck still associated them in the same group of supposed Zoophytes ; 

 his genus was adopted by Blainville and Defrance (vii), who assigned the like place to it ; 

 and it was accepted by many subsequent palaeontologists, as Goldfuss, Michelin, and Bronn, 

 without any question as to its character. By Blainville and Defrance, moreover, another genus, 

 PoJyfrype, was erected upon a mere variety of the same type ; and this also has been accepted 

 as a zoophytic form nearly allied to the preceding. In 1852, however, Bactytopora was included 

 among the Foraminifera by ]M. D'Orbigny (lxxiv) ; who showed, notwithstanding, by the place 

 he assigned to it, a misapprehension of its real nature scarcely less complete than that under 

 which his predecessors had lain ; for he ranks it in his Order Monosfeyues, next to the unilo- 

 cular Ovulites, and says of it : — " C'est une Ovulite egalement percee des deux bouts, pourvue 

 des larges pores places par lignestransverses." How utterly erroneous is this description will 

 appear from the details to be presently given ; yet M. D'Orbigny's authority has given it currency 

 enough to cause it to be accepted by such intelligent palaeontologists as Pictetand Bronn, who, 

 in the latest editions of their respective systematic treatises, have transferred Dactylopora to the 

 place indicated by him, not without the expression of a doubt, however, on the part of the last- 

 named author (x, 'Uebersicht,' p. 25), whether its true place is not among the FistulidcB, in alliance 

 with Synapta and Ilolotlwria, — a suggestion that indicates a perversion of ideas on the subject, 

 for which it is not easy to account. The complex structure of the organism in question was 

 first described, and the interpretation of that structure on the basis of an extended comparison 

 with simpler forms was first given, by Messrs. Parker and Rupert Jones (lxxix) in so unob- 

 trusive a manner as scarcely to challenge the attention which their investigations deserve ; and 

 I gladly avail myself of the opportunity which the present publication affords to give a fuller 

 account, with the requisite illustrations, of this remarkable type, the elucidation of which 

 seems to me not unlikely to lead to a reconsideration of the place assigned to many other 

 organisms at present ranked among Zoophytes or Polyzoa. This account will be chiefly based 

 on the descriptions already given (loc. cit.) by those excellent observers ; but it will depart 

 from these upon several points, as to which the further investigations which we have jointly 

 prosecuted have led to a modification of their original conclusions. The illustrations in Plate X 

 are carefully drawn, by Mr. G. West, from the beautiful series of specimens with which they 

 have furnished me, and which they have kindly allowed me to treat in any manner that I 

 thought desirable for the elucidation of their structure. 



188. External Characters and Internal Structure. — The t3'pe we have now to investigate 

 is one which, like the three preceding, exhibits itself under such a variety of modifications of 

 form, and so many dissimilar phases of development, that only by a careful and extended 



