INVEI^TEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 893 



The Octocoralla or Alcyonaria oifer the simplest conditions ; in 

 correspondence with the eight tentacles ranged round the peristome, 

 the gastric cavity is provided with eight "mesenterial" filaments, 

 which form, in the oral half of the body, gastric filaments, and in the 

 aboral, generative sarcosepta; these eight divisions are the indica- 

 tions of the jiresence of eight parameres, and a half of each forms an 

 anthnere. After a series of considerations of the results attained to 

 by a number of observers, of which it is impossible to present any 

 abstract, the author comes to the conclusion that the body of the 

 Octocoralla is formed of eight unequal parameres, which are so 

 arranged round the primary axis as to give to the body the appearance 

 of a bilateral symmetry ; but the author is careful to point out that 

 this last apjilication is a somewhat wide one, and that all we can 

 justly say is that the Alcyonarian is octampliipleural. 



The Hesacoralla ofler some points of difficulty, inasmuch as the 

 number of their divisions may reach to several hundreds in some 

 forms, and this multiplication of secondary and tertiary systems leads 

 to the difficult question as to whether they each correspond to a para- 

 mere ; if we accept the view that each tentacle corresponds to a para- 

 mere, then if we take such a form as Actinia mescmbrycmthemum, in 

 which there are 192 tentacles, we find that the six largest tentacles of 

 the first cycle correspond to the six largest parameres ; and that they, as 

 well as the next succeeding cycles of 6, 12, 24, and 48 tentacles will 

 be each of them bilaterally symmetrical (eudipleural) ; but as this will 

 not apply to the sixth cycle of 96, in which the proper sarcosepts are 

 not paired, and they consequently would be asymmetrical, it is difficult 

 to see how the view of Koch, by which each tentacle is regarded as 

 corresponding to a paramere, can be substantiated. To this is opposed 

 the view of Professor Haeckel, who regards each paramere as a sixtli of 

 the coral "person," and as made of six interradial (of the second cycle) 

 and of six times thirty-one tentacles, of which the median (pcri-radial) 

 one belongs to the first cycle, and the lateral (adradial) thirty to the 

 3rd, 4th, 5th and 6th cycles respectively. This view appears to recom- 

 mend itself to Dr. Haacke, who finds in EuphjUia spfieniscus the six 

 parameres very distinctly marked out by their coloration. 



In the Tetracoralla there are four parameres. 



As to the development of the different groups, we Imow very littlo 

 as to the stages, subsequent to the gastrula, in the Octocoralla; 

 Kowalewsky's figiires seem to indicate that when the eight parameres 

 are formed, the two lateral are much the larger, and this observation 

 shows how it is possible, although indeed the ellipse-shaped mouth 

 would do just as well, to draw a dorso- ventral median plane through 

 the creature ; similarly, the greater length of two of the gastric fila- 

 ments (Kolliker) in the Pennatulidje, supports the doctrine of the 

 octamphipleural character of the Octocoralla, to which we have 

 already referred. 



There is somewhat more detailed information with regard to the 

 Hcxacoralla. Lacaze-Duthiers has shown that in the gastrula there 

 are first developed two sarcosepts perpendicular to the median plane 

 * Cf. Dnnft's 'Atlas of Corals,' pi. vi. fig. 1. 



