Actinozoan Nature o/'Millepora alcicornls; 355 



irregular-shaped processes of carbonate of lime. The absence 

 of septa and of a columella, and the difference in the size of 

 the calicular openings, caused the mass to be placed with much 

 doubt amongst the Tabulata by those who are familiar with 

 the other genera of that heterogeneous group. And the results 

 of the examination of the soft parts, made under many diffi- 

 culties by the late Prof. L. Agassiz, removed the Millepores 

 from the Actinozoa altogether. He wrote as follows in the 

 'American Journal of Science and Arts,' 2nd series, vol. xxvi. 

 p. 140 (1858) :— " The animals of Milhpora are Hydroid 

 acalephs and not polyps." ..." I have seen in the Tortugas 

 something very unexpected. Millepora is not an Actinoid 

 polyp, but a genuine Hydroid, closely allied to Hydi-actiniay 

 Dana added a note to this statement, " The drawings of Prof. 

 Agassiz which have been sent us for examination are so 

 obviously Hydractinian in most of their characters that no 

 one can question the relation." Alexander Agassiz, in his 

 charming '■ Sea-side Studies ' (2nd edit. 1871) and in corre- 

 spondence with one of us, is satisfied with his father's correct- 

 ness, and gives a drawing of the Hydractinia-lookmg polyp 

 on the surface of Millepora. 



The importance of these statements need not be explained ; 

 and they led L. Agassiz to examine the hard parts of the 

 Tabulata ; and he decided that much of them Avas sclerobasic 

 instead of sclerodermic. It resulted from the general bearing 

 of his researches that the Tabulata and Rugosa were shifted 

 about by succeeding authors according to their belief in them 

 and in the value of the Tabulata as a natural group. The 

 Hydroid nature of Millepora was asserted by the majority 

 of naturalists. 



There was some dissent, however, from this generalization. 

 Milne-Edwards, in his ' Hist. Nat. des Corall.' vol. iii. p. 224, 

 did not consider the facts elucidated by L. Agassiz to be 

 " assez bien connus," and he did not remove the Millepores 

 from his Tabulata. In the third Report on the British Fossil 

 Corals (Brit. Assoc, for Adv. of Science, 1871), one of us 

 wrote as follows in allusion to L. Agassiz's opinions :- — " Now 

 the distinction between the Actinozoa and the Hydrozoa is well 

 marked : in the first the generative apparatus is included in 

 the gastric and perigastric cavities, and in the last the gene- 

 rative and digestive organs are perfectly apart. Every variety 

 of tentacular and disk apparatus may exist in either ; but the 

 external development of the gemmules, ova, and embryonic 

 forms must be recognized before any Coelenterate animal can 

 be associated with the Hydrozoa. Here is the point where 

 Agassiz fails. His researches are only suggestive until the 



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